92 files changed, 18712 insertions, 0 deletions
diff --git a/Modern_Physics_By_G.Aruldas/Chapter1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter1.ipynb
new file mode 100755
index 00000000..483d55f3
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter1.ipynb
@@ -0,0 +1,311 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:467ef5c6562d2c93b60e422b9b9a8c5a34323da84f6c33e87f513c3c578db36d"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "1: The special theory of relativity"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.2, Page number 10"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=1;   #assume\n",
+      "udash=0.9*c;   #speed of 2nd rocket\n",
+      "v=0.6*c;   #speed of 1st rocket\n",
+      "\n",
+      "#Calculation\n",
+      "u1=(udash+v)/(1+(udash*v/(c**2)));   #speed of 2nd rocket in same direction\n",
+      "u2=(-udash+v)/(1-(udash*v/(c**2)));   #speed of 2nd rocket in opposite direction\n",
+      "\n",
+      "#Result\n",
+      "print \"speed of 2nd rocket in same direction is\",round(u1,3),\"*c\"\n",
+      "print \"speed of 2nd rocket in opposite direction is\",round(u2,3),\"*c\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed of 2nd rocket in same direction is 0.974 *c\n",
+        "speed of 2nd rocket in opposite direction is -0.652 *c\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.3, Page number 12"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "#given L0-L/L0=0.01.so L=0.99*L0\n",
+      "LbyL0=0.99;\n",
+      "c=1;   #assume\n",
+      "\n",
+      "#Calculation\n",
+      "v2=(c**2)*(1-(LbyL0)**2);\n",
+      "v=math.sqrt(v2);    #speed\n",
+      "\n",
+      "#Result\n",
+      "print \"speed is\",round(v,3),\"*c\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed is 0.141 *c\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.4, Page number 12"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "delta_tow=2.6*10**-8;   #mean lifetime at rest(s)\n",
+      "d=20;   #distance(m)\n",
+      "c=3*10**8;   #speed of light(m/s)\n",
+      "\n",
+      "#Calculation\n",
+      "#delta_t=d/v\n",
+      "v2=(c**2)/(1+(delta_tow*c/d)**2);\n",
+      "v=math.sqrt(v2);   #speed of unstable particle(m/s)\n",
+      "\n",
+      "#Result\n",
+      "print \"speed of unstable particle is\",round(v/10**8,1),\"*10**8 m/s\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed of unstable particle is 2.8 *10**8 m/s\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.5, Page number 13"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "delta_t=5*10**-6;   #mean lifetime(s)\n",
+      "c=1;   #assume\n",
+      "v=0.9*c;   #speed of beam\n",
+      "\n",
+      "#Calculation\n",
+      "delta_tow=delta_t*math.sqrt(1-(v/c)**2);   #proper lifetime of particles(s)\n",
+      "\n",
+      "#Result\n",
+      "print \"proper lifetime of particles is\",round(delta_tow*10**6,2),\"*10**-6 s\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "proper lifetime of particles is 2.18 *10**-6 s\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.6, Page number 15"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=1;   #assume\n",
+      "m0bym=100/120;    #ratio of masses\n",
+      "\n",
+      "#Calculation\n",
+      "v=c*math.sqrt(1-(m0bym**2));     #speed of body\n",
+      "\n",
+      "#Result\n",
+      "print \"speed of body is\",round(v,3),\"*c\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed of body is 0.553 *c\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.7, Page number 17"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=3*10**8;   #speed of light(m/s)\n",
+      "deltaE=4*10**26;   #energy of sun(J/s)\n",
+      "\n",
+      "#Calculation\n",
+      "deltam=deltaE/c**2;   #change in mass(kg)\n",
+      "\n",
+      "#Result\n",
+      "print \"change in mass is\",round(deltam/10**9,2),\"*10**9 kg\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "change in mass is 4.44 *10**9 kg\n"
+       ]
+      }
+     ],
+     "prompt_number": 13
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.8, Page number 17"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=1;   #assume\n",
+      "T=10;   #kinetic energy(MeV)\n",
+      "m0c2=0.512;   #rest energy of electron(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "E=T+m0c2;   #total energy(MeV)\n",
+      "p=math.sqrt((E**2)-(m0c2**2))/c;    #momentum of electron(MeV/c)\n",
+      "v=c*math.sqrt(1-(m0c2/E)**2);    #velocity of electron(c)\n",
+      "\n",
+      "#Result\n",
+      "print \"momentum of electron is\",round(p,1),\"MeV/c\"\n",
+      "print \"velocity of electron is\",round(v,4),\"*c\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "momentum of electron is 10.5 MeV/c\n",
+        "velocity of electron is 0.9988 *c\n"
+       ]
+      }
+     ],
+     "prompt_number": 16
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter10.ipynb b/Modern_Physics_By_G.Aruldas/Chapter10.ipynb
new file mode 100755
index 00000000..d4104917
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter10.ipynb
@@ -0,0 +1,434 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:de4c224e2d9bad9e810e24de23e4ee016e17fa0ec4d45805b35802744f1cd3b7"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "10: Crystal structure and bonding"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.5, Page number 213"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h1=1;\n",
+      "k1=0;\n",
+      "l1=0;    #for (100) plane\n",
+      "h2=1;\n",
+      "k2=1;\n",
+      "l2=1;    #for (111) plane\n",
+      "a=1;   #assume\n",
+      "\n",
+      "#Calculation\n",
+      "d100=a/math.sqrt(h1**2+k1**2+l1**2);   #spacing between (100) plane\n",
+      "d111=a/math.sqrt(h2**2+k2**2+l2**2);   #spacing between (111) plane\n",
+      "\n",
+      "#Result\n",
+      "print \"spacing between (100) plane is\",d100,\"a\"\n",
+      "print \"spacing between (111) plane is\",round(d111,3),\"a\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "spacing between (100) plane is 1.0 a\n",
+        "spacing between (111) plane is 0.577 a\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.6, Page number 213"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "r=0.152;    #atomic radius(nm)\n",
+      "h1=2;\n",
+      "k1=3;\n",
+      "l1=1;   #for plane (231)\n",
+      "h2=1;\n",
+      "k2=1;\n",
+      "l2=0;    #for plane (110)\n",
+      "\n",
+      "#Calculation\n",
+      "a=4*r/math.sqrt(2);\n",
+      "d231=a/math.sqrt(h1**2+k1**2+l1**2);   #spacing between (231) plane(nm) \n",
+      "d110=a/math.sqrt(h2**2+k2**2+l2**2);   #spacing between (110) plane(nm)\n",
+      "\n",
+      "#Result\n",
+      "print \"spacing between (231) plane is\",round(d231,4),\"nm\"\n",
+      "print \"spacing between (110) plane is\",d110,\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "spacing between (231) plane is 0.1149 nm\n",
+        "spacing between (110) plane is 0.304 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 4
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.7, Page number 213"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=1;\n",
+      "k=0;\n",
+      "l=2;    #for plane (102)\n",
+      "a=0.424;   #edge(nm)\n",
+      "\n",
+      "#Calculation\n",
+      "d102=a/math.sqrt(h**2+k**2+l**2);   #interplanar spacing(nm)\n",
+      "\n",
+      "#Result\n",
+      "print \"interplanar spacing is\",round(d102,4),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "interplanar spacing is 0.1896 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.8, Page number 214"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "a=3.2*10**-10;   #edge(m)\n",
+      "rho=11.36*10**3;   #density(kg/m**3)\n",
+      "N=6.023*10**26;    #avagadro number(per k mol)\n",
+      "M=207.2;   #atomic weight\n",
+      "\n",
+      "#Calculation\n",
+      "n=a**3*rho*N/M;    #number of atoms per unit cell\n",
+      "\n",
+      "#Result\n",
+      "print \"number of atoms per unit cell is\",int(n)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "number of atoms per unit cell is 1\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.9, Page number 220"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "d=2.51*10**-10;    #spacing between planes(m)\n",
+      "theta=9;   #glancing angle(degrees)\n",
+      "\n",
+      "#Calculation\n",
+      "theta=theta*math.pi/180;   #glancing angle(radian)\n",
+      "lamda=2*d*math.sin(theta);  #wavelength(m)\n",
+      "a=lamda/2.51;\n",
+      "theta2=math.asin(a);   #glancing angle for 2nd order diffraction(radian)\n",
+      "theta2=2*theta*180/math.pi;   #glancing angle for 2nd order diffraction(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength of X ray is\",round(lamda*10**10,4),\"angstrom\"\n",
+      "print \"glancing angle for 2nd order diffraction is\",theta2,\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength of X ray is 0.7853 angstrom\n",
+        "glancing angle for 2nd order diffraction is 18.0 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 28
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.10, Page number 220"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "a=5*10**-10;   #lattice parameter(m)\n",
+      "n=1;\n",
+      "lamda=1.4*10**-10;   #wavelength(m)\n",
+      "h=1;\n",
+      "k=1;\n",
+      "l=1;      #for plane (111)\n",
+      "\n",
+      "#Calculation\n",
+      "d111=a/math.sqrt(h**2+k**2+l**2);\n",
+      "b=n*lamda/(2*d111);\n",
+      "theta111=math.asin(b);   #incident angle(radian)\n",
+      "theta111=theta111*180/math.pi;    #incident angle(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"incident angle is\",int(theta111),\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "incident angle is 14 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 30
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.11, Page number 221"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "H=6.626*10**-34;    #planck's constant(Js)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "V=120;   #potential(V)\n",
+      "theta=22;   #angle(degrees)\n",
+      "theta=theta*math.pi/180;   #angle(radian)\n",
+      "h=1;\n",
+      "k=1;\n",
+      "l=1;      #for plane (111)\n",
+      "\n",
+      "#Calculation\n",
+      "x=(2*m*e*V)**(1/2);    \n",
+      "lamda=H/x;      #wavelength(m)\n",
+      "d111=lamda*10**10/(2*math.sin(theta));\n",
+      "a=math.sqrt(h**2+k**2+l**2)*d111;   #lattice parameter(angstrom)\n",
+      "\n",
+      "#Result\n",
+      "print \"lattice parameter is\",round(a,2),\"angstrom\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "lattice parameter is 2.59 angstrom\n"
+       ]
+      }
+     ],
+     "prompt_number": 49
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.12, Page number 224"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "epsilon0=8.85*10**-12;\n",
+      "r0=0.32*10**-9;   #distance(m)\n",
+      "\n",
+      "#Calculation\n",
+      "V=-e/(4*math.pi*epsilon0*r0);   #potential energy(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"potential energy is\",round(V,3),\"eV\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "potential energy is -4.496 eV\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 52
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.13, Page number 224"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "epsilon0=8.85*10**-12;\n",
+      "r0=0.31*10**-9;   #distance(m)\n",
+      "n=9;\n",
+      "alpha=1.748;  \n",
+      "Ie=5;   #ionisation energy(eV)\n",
+      "ea=-3.61;   #electron affinity(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "a=1-(1/n);\n",
+      "Vr0=-alpha*e**2*a/(4*math.pi*epsilon0*r0);   #energy(J)\n",
+      "Vr0=Vr0/e;     #cohesive energy(eV)\n",
+      "Vr0i=Vr0/2;    #contribution per ion to cohesive energy(eV)\n",
+      "Ee=Ie+ea;   #electron transfer energy(eV)\n",
+      "Vr0i2=Ee/2;    #contribution per ion to cohesive energy(eV)\n",
+      "CE=Vr0i+Vr0i2;   #cohesive energy per atom(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"cohesive energy per atom is\",round(CE,4),\"eV\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "cohesive energy per atom is -2.9105 eV\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 58
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter10_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter10_1.ipynb
new file mode 100755
index 00000000..d4104917
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter10_1.ipynb
@@ -0,0 +1,434 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:de4c224e2d9bad9e810e24de23e4ee016e17fa0ec4d45805b35802744f1cd3b7"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "10: Crystal structure and bonding"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.5, Page number 213"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h1=1;\n",
+      "k1=0;\n",
+      "l1=0;    #for (100) plane\n",
+      "h2=1;\n",
+      "k2=1;\n",
+      "l2=1;    #for (111) plane\n",
+      "a=1;   #assume\n",
+      "\n",
+      "#Calculation\n",
+      "d100=a/math.sqrt(h1**2+k1**2+l1**2);   #spacing between (100) plane\n",
+      "d111=a/math.sqrt(h2**2+k2**2+l2**2);   #spacing between (111) plane\n",
+      "\n",
+      "#Result\n",
+      "print \"spacing between (100) plane is\",d100,\"a\"\n",
+      "print \"spacing between (111) plane is\",round(d111,3),\"a\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "spacing between (100) plane is 1.0 a\n",
+        "spacing between (111) plane is 0.577 a\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.6, Page number 213"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "r=0.152;    #atomic radius(nm)\n",
+      "h1=2;\n",
+      "k1=3;\n",
+      "l1=1;   #for plane (231)\n",
+      "h2=1;\n",
+      "k2=1;\n",
+      "l2=0;    #for plane (110)\n",
+      "\n",
+      "#Calculation\n",
+      "a=4*r/math.sqrt(2);\n",
+      "d231=a/math.sqrt(h1**2+k1**2+l1**2);   #spacing between (231) plane(nm) \n",
+      "d110=a/math.sqrt(h2**2+k2**2+l2**2);   #spacing between (110) plane(nm)\n",
+      "\n",
+      "#Result\n",
+      "print \"spacing between (231) plane is\",round(d231,4),\"nm\"\n",
+      "print \"spacing between (110) plane is\",d110,\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "spacing between (231) plane is 0.1149 nm\n",
+        "spacing between (110) plane is 0.304 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 4
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.7, Page number 213"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=1;\n",
+      "k=0;\n",
+      "l=2;    #for plane (102)\n",
+      "a=0.424;   #edge(nm)\n",
+      "\n",
+      "#Calculation\n",
+      "d102=a/math.sqrt(h**2+k**2+l**2);   #interplanar spacing(nm)\n",
+      "\n",
+      "#Result\n",
+      "print \"interplanar spacing is\",round(d102,4),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "interplanar spacing is 0.1896 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.8, Page number 214"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "a=3.2*10**-10;   #edge(m)\n",
+      "rho=11.36*10**3;   #density(kg/m**3)\n",
+      "N=6.023*10**26;    #avagadro number(per k mol)\n",
+      "M=207.2;   #atomic weight\n",
+      "\n",
+      "#Calculation\n",
+      "n=a**3*rho*N/M;    #number of atoms per unit cell\n",
+      "\n",
+      "#Result\n",
+      "print \"number of atoms per unit cell is\",int(n)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "number of atoms per unit cell is 1\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.9, Page number 220"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "d=2.51*10**-10;    #spacing between planes(m)\n",
+      "theta=9;   #glancing angle(degrees)\n",
+      "\n",
+      "#Calculation\n",
+      "theta=theta*math.pi/180;   #glancing angle(radian)\n",
+      "lamda=2*d*math.sin(theta);  #wavelength(m)\n",
+      "a=lamda/2.51;\n",
+      "theta2=math.asin(a);   #glancing angle for 2nd order diffraction(radian)\n",
+      "theta2=2*theta*180/math.pi;   #glancing angle for 2nd order diffraction(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength of X ray is\",round(lamda*10**10,4),\"angstrom\"\n",
+      "print \"glancing angle for 2nd order diffraction is\",theta2,\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength of X ray is 0.7853 angstrom\n",
+        "glancing angle for 2nd order diffraction is 18.0 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 28
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.10, Page number 220"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "a=5*10**-10;   #lattice parameter(m)\n",
+      "n=1;\n",
+      "lamda=1.4*10**-10;   #wavelength(m)\n",
+      "h=1;\n",
+      "k=1;\n",
+      "l=1;      #for plane (111)\n",
+      "\n",
+      "#Calculation\n",
+      "d111=a/math.sqrt(h**2+k**2+l**2);\n",
+      "b=n*lamda/(2*d111);\n",
+      "theta111=math.asin(b);   #incident angle(radian)\n",
+      "theta111=theta111*180/math.pi;    #incident angle(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"incident angle is\",int(theta111),\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "incident angle is 14 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 30
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.11, Page number 221"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "H=6.626*10**-34;    #planck's constant(Js)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "V=120;   #potential(V)\n",
+      "theta=22;   #angle(degrees)\n",
+      "theta=theta*math.pi/180;   #angle(radian)\n",
+      "h=1;\n",
+      "k=1;\n",
+      "l=1;      #for plane (111)\n",
+      "\n",
+      "#Calculation\n",
+      "x=(2*m*e*V)**(1/2);    \n",
+      "lamda=H/x;      #wavelength(m)\n",
+      "d111=lamda*10**10/(2*math.sin(theta));\n",
+      "a=math.sqrt(h**2+k**2+l**2)*d111;   #lattice parameter(angstrom)\n",
+      "\n",
+      "#Result\n",
+      "print \"lattice parameter is\",round(a,2),\"angstrom\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "lattice parameter is 2.59 angstrom\n"
+       ]
+      }
+     ],
+     "prompt_number": 49
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.12, Page number 224"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "epsilon0=8.85*10**-12;\n",
+      "r0=0.32*10**-9;   #distance(m)\n",
+      "\n",
+      "#Calculation\n",
+      "V=-e/(4*math.pi*epsilon0*r0);   #potential energy(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"potential energy is\",round(V,3),\"eV\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "potential energy is -4.496 eV\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 52
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.13, Page number 224"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "epsilon0=8.85*10**-12;\n",
+      "r0=0.31*10**-9;   #distance(m)\n",
+      "n=9;\n",
+      "alpha=1.748;  \n",
+      "Ie=5;   #ionisation energy(eV)\n",
+      "ea=-3.61;   #electron affinity(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "a=1-(1/n);\n",
+      "Vr0=-alpha*e**2*a/(4*math.pi*epsilon0*r0);   #energy(J)\n",
+      "Vr0=Vr0/e;     #cohesive energy(eV)\n",
+      "Vr0i=Vr0/2;    #contribution per ion to cohesive energy(eV)\n",
+      "Ee=Ie+ea;   #electron transfer energy(eV)\n",
+      "Vr0i2=Ee/2;    #contribution per ion to cohesive energy(eV)\n",
+      "CE=Vr0i+Vr0i2;   #cohesive energy per atom(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"cohesive energy per atom is\",round(CE,4),\"eV\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "cohesive energy per atom is -2.9105 eV\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 58
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter10_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter10_2.ipynb
new file mode 100755
index 00000000..d4104917
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter10_2.ipynb
@@ -0,0 +1,434 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:de4c224e2d9bad9e810e24de23e4ee016e17fa0ec4d45805b35802744f1cd3b7"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "10: Crystal structure and bonding"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.5, Page number 213"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h1=1;\n",
+      "k1=0;\n",
+      "l1=0;    #for (100) plane\n",
+      "h2=1;\n",
+      "k2=1;\n",
+      "l2=1;    #for (111) plane\n",
+      "a=1;   #assume\n",
+      "\n",
+      "#Calculation\n",
+      "d100=a/math.sqrt(h1**2+k1**2+l1**2);   #spacing between (100) plane\n",
+      "d111=a/math.sqrt(h2**2+k2**2+l2**2);   #spacing between (111) plane\n",
+      "\n",
+      "#Result\n",
+      "print \"spacing between (100) plane is\",d100,\"a\"\n",
+      "print \"spacing between (111) plane is\",round(d111,3),\"a\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "spacing between (100) plane is 1.0 a\n",
+        "spacing between (111) plane is 0.577 a\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.6, Page number 213"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "r=0.152;    #atomic radius(nm)\n",
+      "h1=2;\n",
+      "k1=3;\n",
+      "l1=1;   #for plane (231)\n",
+      "h2=1;\n",
+      "k2=1;\n",
+      "l2=0;    #for plane (110)\n",
+      "\n",
+      "#Calculation\n",
+      "a=4*r/math.sqrt(2);\n",
+      "d231=a/math.sqrt(h1**2+k1**2+l1**2);   #spacing between (231) plane(nm) \n",
+      "d110=a/math.sqrt(h2**2+k2**2+l2**2);   #spacing between (110) plane(nm)\n",
+      "\n",
+      "#Result\n",
+      "print \"spacing between (231) plane is\",round(d231,4),\"nm\"\n",
+      "print \"spacing between (110) plane is\",d110,\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "spacing between (231) plane is 0.1149 nm\n",
+        "spacing between (110) plane is 0.304 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 4
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.7, Page number 213"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=1;\n",
+      "k=0;\n",
+      "l=2;    #for plane (102)\n",
+      "a=0.424;   #edge(nm)\n",
+      "\n",
+      "#Calculation\n",
+      "d102=a/math.sqrt(h**2+k**2+l**2);   #interplanar spacing(nm)\n",
+      "\n",
+      "#Result\n",
+      "print \"interplanar spacing is\",round(d102,4),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "interplanar spacing is 0.1896 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.8, Page number 214"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "a=3.2*10**-10;   #edge(m)\n",
+      "rho=11.36*10**3;   #density(kg/m**3)\n",
+      "N=6.023*10**26;    #avagadro number(per k mol)\n",
+      "M=207.2;   #atomic weight\n",
+      "\n",
+      "#Calculation\n",
+      "n=a**3*rho*N/M;    #number of atoms per unit cell\n",
+      "\n",
+      "#Result\n",
+      "print \"number of atoms per unit cell is\",int(n)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "number of atoms per unit cell is 1\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.9, Page number 220"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "d=2.51*10**-10;    #spacing between planes(m)\n",
+      "theta=9;   #glancing angle(degrees)\n",
+      "\n",
+      "#Calculation\n",
+      "theta=theta*math.pi/180;   #glancing angle(radian)\n",
+      "lamda=2*d*math.sin(theta);  #wavelength(m)\n",
+      "a=lamda/2.51;\n",
+      "theta2=math.asin(a);   #glancing angle for 2nd order diffraction(radian)\n",
+      "theta2=2*theta*180/math.pi;   #glancing angle for 2nd order diffraction(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength of X ray is\",round(lamda*10**10,4),\"angstrom\"\n",
+      "print \"glancing angle for 2nd order diffraction is\",theta2,\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength of X ray is 0.7853 angstrom\n",
+        "glancing angle for 2nd order diffraction is 18.0 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 28
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.10, Page number 220"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "a=5*10**-10;   #lattice parameter(m)\n",
+      "n=1;\n",
+      "lamda=1.4*10**-10;   #wavelength(m)\n",
+      "h=1;\n",
+      "k=1;\n",
+      "l=1;      #for plane (111)\n",
+      "\n",
+      "#Calculation\n",
+      "d111=a/math.sqrt(h**2+k**2+l**2);\n",
+      "b=n*lamda/(2*d111);\n",
+      "theta111=math.asin(b);   #incident angle(radian)\n",
+      "theta111=theta111*180/math.pi;    #incident angle(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"incident angle is\",int(theta111),\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "incident angle is 14 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 30
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.11, Page number 221"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "H=6.626*10**-34;    #planck's constant(Js)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "V=120;   #potential(V)\n",
+      "theta=22;   #angle(degrees)\n",
+      "theta=theta*math.pi/180;   #angle(radian)\n",
+      "h=1;\n",
+      "k=1;\n",
+      "l=1;      #for plane (111)\n",
+      "\n",
+      "#Calculation\n",
+      "x=(2*m*e*V)**(1/2);    \n",
+      "lamda=H/x;      #wavelength(m)\n",
+      "d111=lamda*10**10/(2*math.sin(theta));\n",
+      "a=math.sqrt(h**2+k**2+l**2)*d111;   #lattice parameter(angstrom)\n",
+      "\n",
+      "#Result\n",
+      "print \"lattice parameter is\",round(a,2),\"angstrom\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "lattice parameter is 2.59 angstrom\n"
+       ]
+      }
+     ],
+     "prompt_number": 49
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.12, Page number 224"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "epsilon0=8.85*10**-12;\n",
+      "r0=0.32*10**-9;   #distance(m)\n",
+      "\n",
+      "#Calculation\n",
+      "V=-e/(4*math.pi*epsilon0*r0);   #potential energy(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"potential energy is\",round(V,3),\"eV\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "potential energy is -4.496 eV\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 52
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.13, Page number 224"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "epsilon0=8.85*10**-12;\n",
+      "r0=0.31*10**-9;   #distance(m)\n",
+      "n=9;\n",
+      "alpha=1.748;  \n",
+      "Ie=5;   #ionisation energy(eV)\n",
+      "ea=-3.61;   #electron affinity(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "a=1-(1/n);\n",
+      "Vr0=-alpha*e**2*a/(4*math.pi*epsilon0*r0);   #energy(J)\n",
+      "Vr0=Vr0/e;     #cohesive energy(eV)\n",
+      "Vr0i=Vr0/2;    #contribution per ion to cohesive energy(eV)\n",
+      "Ee=Ie+ea;   #electron transfer energy(eV)\n",
+      "Vr0i2=Ee/2;    #contribution per ion to cohesive energy(eV)\n",
+      "CE=Vr0i+Vr0i2;   #cohesive energy per atom(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"cohesive energy per atom is\",round(CE,4),\"eV\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "cohesive energy per atom is -2.9105 eV\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 58
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter10_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter10_3.ipynb
new file mode 100755
index 00000000..d4104917
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter10_3.ipynb
@@ -0,0 +1,434 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:de4c224e2d9bad9e810e24de23e4ee016e17fa0ec4d45805b35802744f1cd3b7"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "10: Crystal structure and bonding"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.5, Page number 213"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h1=1;\n",
+      "k1=0;\n",
+      "l1=0;    #for (100) plane\n",
+      "h2=1;\n",
+      "k2=1;\n",
+      "l2=1;    #for (111) plane\n",
+      "a=1;   #assume\n",
+      "\n",
+      "#Calculation\n",
+      "d100=a/math.sqrt(h1**2+k1**2+l1**2);   #spacing between (100) plane\n",
+      "d111=a/math.sqrt(h2**2+k2**2+l2**2);   #spacing between (111) plane\n",
+      "\n",
+      "#Result\n",
+      "print \"spacing between (100) plane is\",d100,\"a\"\n",
+      "print \"spacing between (111) plane is\",round(d111,3),\"a\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "spacing between (100) plane is 1.0 a\n",
+        "spacing between (111) plane is 0.577 a\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.6, Page number 213"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "r=0.152;    #atomic radius(nm)\n",
+      "h1=2;\n",
+      "k1=3;\n",
+      "l1=1;   #for plane (231)\n",
+      "h2=1;\n",
+      "k2=1;\n",
+      "l2=0;    #for plane (110)\n",
+      "\n",
+      "#Calculation\n",
+      "a=4*r/math.sqrt(2);\n",
+      "d231=a/math.sqrt(h1**2+k1**2+l1**2);   #spacing between (231) plane(nm) \n",
+      "d110=a/math.sqrt(h2**2+k2**2+l2**2);   #spacing between (110) plane(nm)\n",
+      "\n",
+      "#Result\n",
+      "print \"spacing between (231) plane is\",round(d231,4),\"nm\"\n",
+      "print \"spacing between (110) plane is\",d110,\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "spacing between (231) plane is 0.1149 nm\n",
+        "spacing between (110) plane is 0.304 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 4
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.7, Page number 213"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=1;\n",
+      "k=0;\n",
+      "l=2;    #for plane (102)\n",
+      "a=0.424;   #edge(nm)\n",
+      "\n",
+      "#Calculation\n",
+      "d102=a/math.sqrt(h**2+k**2+l**2);   #interplanar spacing(nm)\n",
+      "\n",
+      "#Result\n",
+      "print \"interplanar spacing is\",round(d102,4),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "interplanar spacing is 0.1896 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.8, Page number 214"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "a=3.2*10**-10;   #edge(m)\n",
+      "rho=11.36*10**3;   #density(kg/m**3)\n",
+      "N=6.023*10**26;    #avagadro number(per k mol)\n",
+      "M=207.2;   #atomic weight\n",
+      "\n",
+      "#Calculation\n",
+      "n=a**3*rho*N/M;    #number of atoms per unit cell\n",
+      "\n",
+      "#Result\n",
+      "print \"number of atoms per unit cell is\",int(n)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "number of atoms per unit cell is 1\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.9, Page number 220"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "d=2.51*10**-10;    #spacing between planes(m)\n",
+      "theta=9;   #glancing angle(degrees)\n",
+      "\n",
+      "#Calculation\n",
+      "theta=theta*math.pi/180;   #glancing angle(radian)\n",
+      "lamda=2*d*math.sin(theta);  #wavelength(m)\n",
+      "a=lamda/2.51;\n",
+      "theta2=math.asin(a);   #glancing angle for 2nd order diffraction(radian)\n",
+      "theta2=2*theta*180/math.pi;   #glancing angle for 2nd order diffraction(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength of X ray is\",round(lamda*10**10,4),\"angstrom\"\n",
+      "print \"glancing angle for 2nd order diffraction is\",theta2,\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength of X ray is 0.7853 angstrom\n",
+        "glancing angle for 2nd order diffraction is 18.0 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 28
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.10, Page number 220"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "a=5*10**-10;   #lattice parameter(m)\n",
+      "n=1;\n",
+      "lamda=1.4*10**-10;   #wavelength(m)\n",
+      "h=1;\n",
+      "k=1;\n",
+      "l=1;      #for plane (111)\n",
+      "\n",
+      "#Calculation\n",
+      "d111=a/math.sqrt(h**2+k**2+l**2);\n",
+      "b=n*lamda/(2*d111);\n",
+      "theta111=math.asin(b);   #incident angle(radian)\n",
+      "theta111=theta111*180/math.pi;    #incident angle(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"incident angle is\",int(theta111),\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "incident angle is 14 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 30
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.11, Page number 221"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "H=6.626*10**-34;    #planck's constant(Js)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "V=120;   #potential(V)\n",
+      "theta=22;   #angle(degrees)\n",
+      "theta=theta*math.pi/180;   #angle(radian)\n",
+      "h=1;\n",
+      "k=1;\n",
+      "l=1;      #for plane (111)\n",
+      "\n",
+      "#Calculation\n",
+      "x=(2*m*e*V)**(1/2);    \n",
+      "lamda=H/x;      #wavelength(m)\n",
+      "d111=lamda*10**10/(2*math.sin(theta));\n",
+      "a=math.sqrt(h**2+k**2+l**2)*d111;   #lattice parameter(angstrom)\n",
+      "\n",
+      "#Result\n",
+      "print \"lattice parameter is\",round(a,2),\"angstrom\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "lattice parameter is 2.59 angstrom\n"
+       ]
+      }
+     ],
+     "prompt_number": 49
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.12, Page number 224"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "epsilon0=8.85*10**-12;\n",
+      "r0=0.32*10**-9;   #distance(m)\n",
+      "\n",
+      "#Calculation\n",
+      "V=-e/(4*math.pi*epsilon0*r0);   #potential energy(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"potential energy is\",round(V,3),\"eV\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "potential energy is -4.496 eV\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 52
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 10.13, Page number 224"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "epsilon0=8.85*10**-12;\n",
+      "r0=0.31*10**-9;   #distance(m)\n",
+      "n=9;\n",
+      "alpha=1.748;  \n",
+      "Ie=5;   #ionisation energy(eV)\n",
+      "ea=-3.61;   #electron affinity(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "a=1-(1/n);\n",
+      "Vr0=-alpha*e**2*a/(4*math.pi*epsilon0*r0);   #energy(J)\n",
+      "Vr0=Vr0/e;     #cohesive energy(eV)\n",
+      "Vr0i=Vr0/2;    #contribution per ion to cohesive energy(eV)\n",
+      "Ee=Ie+ea;   #electron transfer energy(eV)\n",
+      "Vr0i2=Ee/2;    #contribution per ion to cohesive energy(eV)\n",
+      "CE=Vr0i+Vr0i2;   #cohesive energy per atom(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"cohesive energy per atom is\",round(CE,4),\"eV\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "cohesive energy per atom is -2.9105 eV\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 58
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter11.ipynb b/Modern_Physics_By_G.Aruldas/Chapter11.ipynb
new file mode 100755
index 00000000..ffdec850
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter11.ipynb
@@ -0,0 +1,114 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:df9996e09d849b24524dd415b626cbe4279b4acdbe25d68bb407e2d42467c7a7"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "11: Lattice dynamics"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 11.1, Page number 238"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "thetaD=350;    #temperature for Cu(K)\n",
+      "theetaD=550;   #temperature for Si(K)\n",
+      "\n",
+      "#Calculation\n",
+      "newDCu=k*thetaD/h;   #highest possible frequency for Cu(per sec)\n",
+      "newDSi=k*theetaD/h;  #highest possible frequency for Si(per sec)\n",
+      "\n",
+      "#Result\n",
+      "print \"highest possible frequency for Cu is\",round(newDCu/10**11,3),\"*10**11 per sec\"\n",
+      "print \"highest possible frequency for Si is\",round(newDSi/10**11,2),\"*10**11 per sec\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "highest possible frequency for Cu is 72.895 *10**11 per sec\n",
+        "highest possible frequency for Si is 114.55 *10**11 per sec\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 11.2, Page number 238"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "N=6.02*10**26;   #avagadro number(k/mole)\n",
+      "T=10;   #temperature(K)\n",
+      "thetaD=105;   #debye temperature(K)\n",
+      "\n",
+      "#Calculation\n",
+      "C=(12/5)*(math.pi**4)*N*k*(T/thetaD)**3;   #specific heat of lead(J/K kmol)\n",
+      "newD=k*thetaD/h;    #highest frequency(per sec)\n",
+      "\n",
+      "#Result\n",
+      "print \"specific heat of lead is\",round(C,1),\"J/K kmol\"\n",
+      "print \"answer varies due to rounding off errors\"\n",
+      "print \"highest frequency is\",round(newD/10**11,2),\"*10**11 per sec\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "specific heat of lead is 1677.7 J/K kmol\n",
+        "answer varies due to rounding off errors\n",
+        "highest frequency is 21.87 *10**11 per sec\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter11_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter11_1.ipynb
new file mode 100755
index 00000000..ffdec850
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter11_1.ipynb
@@ -0,0 +1,114 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:df9996e09d849b24524dd415b626cbe4279b4acdbe25d68bb407e2d42467c7a7"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "11: Lattice dynamics"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 11.1, Page number 238"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "thetaD=350;    #temperature for Cu(K)\n",
+      "theetaD=550;   #temperature for Si(K)\n",
+      "\n",
+      "#Calculation\n",
+      "newDCu=k*thetaD/h;   #highest possible frequency for Cu(per sec)\n",
+      "newDSi=k*theetaD/h;  #highest possible frequency for Si(per sec)\n",
+      "\n",
+      "#Result\n",
+      "print \"highest possible frequency for Cu is\",round(newDCu/10**11,3),\"*10**11 per sec\"\n",
+      "print \"highest possible frequency for Si is\",round(newDSi/10**11,2),\"*10**11 per sec\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "highest possible frequency for Cu is 72.895 *10**11 per sec\n",
+        "highest possible frequency for Si is 114.55 *10**11 per sec\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 11.2, Page number 238"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "N=6.02*10**26;   #avagadro number(k/mole)\n",
+      "T=10;   #temperature(K)\n",
+      "thetaD=105;   #debye temperature(K)\n",
+      "\n",
+      "#Calculation\n",
+      "C=(12/5)*(math.pi**4)*N*k*(T/thetaD)**3;   #specific heat of lead(J/K kmol)\n",
+      "newD=k*thetaD/h;    #highest frequency(per sec)\n",
+      "\n",
+      "#Result\n",
+      "print \"specific heat of lead is\",round(C,1),\"J/K kmol\"\n",
+      "print \"answer varies due to rounding off errors\"\n",
+      "print \"highest frequency is\",round(newD/10**11,2),\"*10**11 per sec\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "specific heat of lead is 1677.7 J/K kmol\n",
+        "answer varies due to rounding off errors\n",
+        "highest frequency is 21.87 *10**11 per sec\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter11_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter11_2.ipynb
new file mode 100755
index 00000000..ffdec850
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter11_2.ipynb
@@ -0,0 +1,114 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:df9996e09d849b24524dd415b626cbe4279b4acdbe25d68bb407e2d42467c7a7"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "11: Lattice dynamics"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 11.1, Page number 238"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "thetaD=350;    #temperature for Cu(K)\n",
+      "theetaD=550;   #temperature for Si(K)\n",
+      "\n",
+      "#Calculation\n",
+      "newDCu=k*thetaD/h;   #highest possible frequency for Cu(per sec)\n",
+      "newDSi=k*theetaD/h;  #highest possible frequency for Si(per sec)\n",
+      "\n",
+      "#Result\n",
+      "print \"highest possible frequency for Cu is\",round(newDCu/10**11,3),\"*10**11 per sec\"\n",
+      "print \"highest possible frequency for Si is\",round(newDSi/10**11,2),\"*10**11 per sec\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "highest possible frequency for Cu is 72.895 *10**11 per sec\n",
+        "highest possible frequency for Si is 114.55 *10**11 per sec\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 11.2, Page number 238"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "N=6.02*10**26;   #avagadro number(k/mole)\n",
+      "T=10;   #temperature(K)\n",
+      "thetaD=105;   #debye temperature(K)\n",
+      "\n",
+      "#Calculation\n",
+      "C=(12/5)*(math.pi**4)*N*k*(T/thetaD)**3;   #specific heat of lead(J/K kmol)\n",
+      "newD=k*thetaD/h;    #highest frequency(per sec)\n",
+      "\n",
+      "#Result\n",
+      "print \"specific heat of lead is\",round(C,1),\"J/K kmol\"\n",
+      "print \"answer varies due to rounding off errors\"\n",
+      "print \"highest frequency is\",round(newD/10**11,2),\"*10**11 per sec\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "specific heat of lead is 1677.7 J/K kmol\n",
+        "answer varies due to rounding off errors\n",
+        "highest frequency is 21.87 *10**11 per sec\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter11_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter11_3.ipynb
new file mode 100755
index 00000000..ffdec850
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter11_3.ipynb
@@ -0,0 +1,114 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:df9996e09d849b24524dd415b626cbe4279b4acdbe25d68bb407e2d42467c7a7"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "11: Lattice dynamics"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 11.1, Page number 238"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "thetaD=350;    #temperature for Cu(K)\n",
+      "theetaD=550;   #temperature for Si(K)\n",
+      "\n",
+      "#Calculation\n",
+      "newDCu=k*thetaD/h;   #highest possible frequency for Cu(per sec)\n",
+      "newDSi=k*theetaD/h;  #highest possible frequency for Si(per sec)\n",
+      "\n",
+      "#Result\n",
+      "print \"highest possible frequency for Cu is\",round(newDCu/10**11,3),\"*10**11 per sec\"\n",
+      "print \"highest possible frequency for Si is\",round(newDSi/10**11,2),\"*10**11 per sec\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "highest possible frequency for Cu is 72.895 *10**11 per sec\n",
+        "highest possible frequency for Si is 114.55 *10**11 per sec\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 11.2, Page number 238"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "N=6.02*10**26;   #avagadro number(k/mole)\n",
+      "T=10;   #temperature(K)\n",
+      "thetaD=105;   #debye temperature(K)\n",
+      "\n",
+      "#Calculation\n",
+      "C=(12/5)*(math.pi**4)*N*k*(T/thetaD)**3;   #specific heat of lead(J/K kmol)\n",
+      "newD=k*thetaD/h;    #highest frequency(per sec)\n",
+      "\n",
+      "#Result\n",
+      "print \"specific heat of lead is\",round(C,1),\"J/K kmol\"\n",
+      "print \"answer varies due to rounding off errors\"\n",
+      "print \"highest frequency is\",round(newD/10**11,2),\"*10**11 per sec\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "specific heat of lead is 1677.7 J/K kmol\n",
+        "answer varies due to rounding off errors\n",
+        "highest frequency is 21.87 *10**11 per sec\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter12.ipynb b/Modern_Physics_By_G.Aruldas/Chapter12.ipynb
new file mode 100755
index 00000000..b3818649
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter12.ipynb
@@ -0,0 +1,285 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:881432a5cd98267b92bdfa11e021925fdef61ae98abdadccafbf254c6f9ca038"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "12: Band theory of solids"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.1, Page number 243"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "EF=8;     #fermi energy(eV)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "E0bar=3*EF/5;   \n",
+      "v=math.sqrt(2*E0bar*e/m);     #speed of electron(m/s)\n",
+      "\n",
+      "#Result\n",
+      "print \"speed of electron is\",round(v/10**6,1),\"*10**6 m/s\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed of electron is 1.3 *10**6 m/s\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.2, Page number 244"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "I=8;    #current(ampere)\n",
+      "r=9*10**-4;   #radius(m)\n",
+      "V=5;   #potential difference(V)\n",
+      "L=1;   #length(m)\n",
+      "\n",
+      "#Calculation\n",
+      "A=math.pi*r**2;    #area of wire(m**2)\n",
+      "E=V/L;\n",
+      "J=I/A;   #current density(V/m)\n",
+      "rho=E/J;    #resistivity(ohm m)\n",
+      "\n",
+      "#Result\n",
+      "print \"current density is\",round(J/10**6,3),\"*10**6 V/m\"\n",
+      "print \"resistivity is\",round(rho*10**6,2),\"*10**-6 ohm m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "current density is 3.144 *10**6 V/m\n",
+        "resistivity is 1.59 *10**-6 ohm m\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.3, Page number 245"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "n=1;\n",
+      "a=4*10**-10;   #lattice parameter(m)\n",
+      "N=1.56*10**28;  \n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "tow=10**-15;    #collision time(s)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "N=n/(a**3);    #number of electrons per unit volume(per m**3)\n",
+      "sigma=N*e**2*tow/m;   #conductivity(per ohm m)\n",
+      "rho=1/sigma;   #resistivity(ohm m)\n",
+      "\n",
+      "#Result\n",
+      "print \"conductivity is\",round(sigma/10**6,2),\"*10**6 ohm m\"\n",
+      "print \"resistivity is\",rho,\"ohm m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "conductivity is 0.44 *10**6 ohm m\n",
+        "resistivity is 2.275e-06 ohm m\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.4, Page number 247"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "NA=6.02*10**26;   #avagadro number(k/mole)\n",
+      "T=300;     #temperature(K)\n",
+      "EF=2;   #fermi energy(eV)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "C=math.pi**2*k**2*NA*T/(2*EF*e);    #electronic specific heat(J/kmol/K)\n",
+      "\n",
+      "#Result\n",
+      "print \"electronic specific heat is\",int(C),\"J/kmol/K\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "electronic specific heat is 530 J/kmol/K\n"
+       ]
+      }
+     ],
+     "prompt_number": 10
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.5, Page number 247"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "K=327;    #thermal conductivity(W/mK)\n",
+      "T=300;   #temperature(K)\n",
+      "rho=7.13*10**3;    #density(kg/m**3)\n",
+      "NA=6.02*10**26;   #avagadro number(k/mole)\n",
+      "w=65.38;   #atomic weight\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "tow=2.5*10**-14;   #relaxation time(s)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "N=2*rho*NA/w;     #number of electrons per unit volume(per m**3)\n",
+      "sigma=N*e**2*tow/m;   #conductivity(per ohm m)\n",
+      "L=K/(sigma*T);    #lorentz number(W ohm/K**2)\n",
+      "\n",
+      "#Result\n",
+      "print \"lorentz number is\",round(L*10**8,4),\"*10**-8 W ohm/K**2\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "lorentz number is 1.1804 *10**-8 W ohm/K**2\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.6, Page number 248"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "n=5*10**28;    #number of atoms(/m**3)\n",
+      "\n",
+      "#Calculation\n",
+      "RH=-1/(n*e);    #hall coefficient(m**3/C)\n",
+      "\n",
+      "#Result\n",
+      "print \"hall coefficient is\",round(RH*10**9,3),\"*10**-9 m**3/C\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "hall coefficient is -0.125 *10**-9 m**3/C\n"
+       ]
+      }
+     ],
+     "prompt_number": 14
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter12_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter12_1.ipynb
new file mode 100755
index 00000000..b3818649
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter12_1.ipynb
@@ -0,0 +1,285 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:881432a5cd98267b92bdfa11e021925fdef61ae98abdadccafbf254c6f9ca038"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "12: Band theory of solids"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.1, Page number 243"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "EF=8;     #fermi energy(eV)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "E0bar=3*EF/5;   \n",
+      "v=math.sqrt(2*E0bar*e/m);     #speed of electron(m/s)\n",
+      "\n",
+      "#Result\n",
+      "print \"speed of electron is\",round(v/10**6,1),\"*10**6 m/s\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed of electron is 1.3 *10**6 m/s\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.2, Page number 244"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "I=8;    #current(ampere)\n",
+      "r=9*10**-4;   #radius(m)\n",
+      "V=5;   #potential difference(V)\n",
+      "L=1;   #length(m)\n",
+      "\n",
+      "#Calculation\n",
+      "A=math.pi*r**2;    #area of wire(m**2)\n",
+      "E=V/L;\n",
+      "J=I/A;   #current density(V/m)\n",
+      "rho=E/J;    #resistivity(ohm m)\n",
+      "\n",
+      "#Result\n",
+      "print \"current density is\",round(J/10**6,3),\"*10**6 V/m\"\n",
+      "print \"resistivity is\",round(rho*10**6,2),\"*10**-6 ohm m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "current density is 3.144 *10**6 V/m\n",
+        "resistivity is 1.59 *10**-6 ohm m\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.3, Page number 245"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "n=1;\n",
+      "a=4*10**-10;   #lattice parameter(m)\n",
+      "N=1.56*10**28;  \n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "tow=10**-15;    #collision time(s)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "N=n/(a**3);    #number of electrons per unit volume(per m**3)\n",
+      "sigma=N*e**2*tow/m;   #conductivity(per ohm m)\n",
+      "rho=1/sigma;   #resistivity(ohm m)\n",
+      "\n",
+      "#Result\n",
+      "print \"conductivity is\",round(sigma/10**6,2),\"*10**6 ohm m\"\n",
+      "print \"resistivity is\",rho,\"ohm m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "conductivity is 0.44 *10**6 ohm m\n",
+        "resistivity is 2.275e-06 ohm m\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.4, Page number 247"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "NA=6.02*10**26;   #avagadro number(k/mole)\n",
+      "T=300;     #temperature(K)\n",
+      "EF=2;   #fermi energy(eV)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "C=math.pi**2*k**2*NA*T/(2*EF*e);    #electronic specific heat(J/kmol/K)\n",
+      "\n",
+      "#Result\n",
+      "print \"electronic specific heat is\",int(C),\"J/kmol/K\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "electronic specific heat is 530 J/kmol/K\n"
+       ]
+      }
+     ],
+     "prompt_number": 10
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.5, Page number 247"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "K=327;    #thermal conductivity(W/mK)\n",
+      "T=300;   #temperature(K)\n",
+      "rho=7.13*10**3;    #density(kg/m**3)\n",
+      "NA=6.02*10**26;   #avagadro number(k/mole)\n",
+      "w=65.38;   #atomic weight\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "tow=2.5*10**-14;   #relaxation time(s)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "N=2*rho*NA/w;     #number of electrons per unit volume(per m**3)\n",
+      "sigma=N*e**2*tow/m;   #conductivity(per ohm m)\n",
+      "L=K/(sigma*T);    #lorentz number(W ohm/K**2)\n",
+      "\n",
+      "#Result\n",
+      "print \"lorentz number is\",round(L*10**8,4),\"*10**-8 W ohm/K**2\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "lorentz number is 1.1804 *10**-8 W ohm/K**2\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.6, Page number 248"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "n=5*10**28;    #number of atoms(/m**3)\n",
+      "\n",
+      "#Calculation\n",
+      "RH=-1/(n*e);    #hall coefficient(m**3/C)\n",
+      "\n",
+      "#Result\n",
+      "print \"hall coefficient is\",round(RH*10**9,3),\"*10**-9 m**3/C\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "hall coefficient is -0.125 *10**-9 m**3/C\n"
+       ]
+      }
+     ],
+     "prompt_number": 14
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter12_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter12_2.ipynb
new file mode 100755
index 00000000..b3818649
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter12_2.ipynb
@@ -0,0 +1,285 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:881432a5cd98267b92bdfa11e021925fdef61ae98abdadccafbf254c6f9ca038"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "12: Band theory of solids"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.1, Page number 243"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "EF=8;     #fermi energy(eV)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "E0bar=3*EF/5;   \n",
+      "v=math.sqrt(2*E0bar*e/m);     #speed of electron(m/s)\n",
+      "\n",
+      "#Result\n",
+      "print \"speed of electron is\",round(v/10**6,1),\"*10**6 m/s\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed of electron is 1.3 *10**6 m/s\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.2, Page number 244"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "I=8;    #current(ampere)\n",
+      "r=9*10**-4;   #radius(m)\n",
+      "V=5;   #potential difference(V)\n",
+      "L=1;   #length(m)\n",
+      "\n",
+      "#Calculation\n",
+      "A=math.pi*r**2;    #area of wire(m**2)\n",
+      "E=V/L;\n",
+      "J=I/A;   #current density(V/m)\n",
+      "rho=E/J;    #resistivity(ohm m)\n",
+      "\n",
+      "#Result\n",
+      "print \"current density is\",round(J/10**6,3),\"*10**6 V/m\"\n",
+      "print \"resistivity is\",round(rho*10**6,2),\"*10**-6 ohm m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "current density is 3.144 *10**6 V/m\n",
+        "resistivity is 1.59 *10**-6 ohm m\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.3, Page number 245"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "n=1;\n",
+      "a=4*10**-10;   #lattice parameter(m)\n",
+      "N=1.56*10**28;  \n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "tow=10**-15;    #collision time(s)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "N=n/(a**3);    #number of electrons per unit volume(per m**3)\n",
+      "sigma=N*e**2*tow/m;   #conductivity(per ohm m)\n",
+      "rho=1/sigma;   #resistivity(ohm m)\n",
+      "\n",
+      "#Result\n",
+      "print \"conductivity is\",round(sigma/10**6,2),\"*10**6 ohm m\"\n",
+      "print \"resistivity is\",rho,\"ohm m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "conductivity is 0.44 *10**6 ohm m\n",
+        "resistivity is 2.275e-06 ohm m\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.4, Page number 247"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "NA=6.02*10**26;   #avagadro number(k/mole)\n",
+      "T=300;     #temperature(K)\n",
+      "EF=2;   #fermi energy(eV)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "C=math.pi**2*k**2*NA*T/(2*EF*e);    #electronic specific heat(J/kmol/K)\n",
+      "\n",
+      "#Result\n",
+      "print \"electronic specific heat is\",int(C),\"J/kmol/K\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "electronic specific heat is 530 J/kmol/K\n"
+       ]
+      }
+     ],
+     "prompt_number": 10
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.5, Page number 247"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "K=327;    #thermal conductivity(W/mK)\n",
+      "T=300;   #temperature(K)\n",
+      "rho=7.13*10**3;    #density(kg/m**3)\n",
+      "NA=6.02*10**26;   #avagadro number(k/mole)\n",
+      "w=65.38;   #atomic weight\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "tow=2.5*10**-14;   #relaxation time(s)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "N=2*rho*NA/w;     #number of electrons per unit volume(per m**3)\n",
+      "sigma=N*e**2*tow/m;   #conductivity(per ohm m)\n",
+      "L=K/(sigma*T);    #lorentz number(W ohm/K**2)\n",
+      "\n",
+      "#Result\n",
+      "print \"lorentz number is\",round(L*10**8,4),\"*10**-8 W ohm/K**2\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "lorentz number is 1.1804 *10**-8 W ohm/K**2\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.6, Page number 248"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "n=5*10**28;    #number of atoms(/m**3)\n",
+      "\n",
+      "#Calculation\n",
+      "RH=-1/(n*e);    #hall coefficient(m**3/C)\n",
+      "\n",
+      "#Result\n",
+      "print \"hall coefficient is\",round(RH*10**9,3),\"*10**-9 m**3/C\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "hall coefficient is -0.125 *10**-9 m**3/C\n"
+       ]
+      }
+     ],
+     "prompt_number": 14
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter12_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter12_3.ipynb
new file mode 100755
index 00000000..b3818649
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter12_3.ipynb
@@ -0,0 +1,285 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:881432a5cd98267b92bdfa11e021925fdef61ae98abdadccafbf254c6f9ca038"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "12: Band theory of solids"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.1, Page number 243"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "EF=8;     #fermi energy(eV)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "E0bar=3*EF/5;   \n",
+      "v=math.sqrt(2*E0bar*e/m);     #speed of electron(m/s)\n",
+      "\n",
+      "#Result\n",
+      "print \"speed of electron is\",round(v/10**6,1),\"*10**6 m/s\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed of electron is 1.3 *10**6 m/s\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.2, Page number 244"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "I=8;    #current(ampere)\n",
+      "r=9*10**-4;   #radius(m)\n",
+      "V=5;   #potential difference(V)\n",
+      "L=1;   #length(m)\n",
+      "\n",
+      "#Calculation\n",
+      "A=math.pi*r**2;    #area of wire(m**2)\n",
+      "E=V/L;\n",
+      "J=I/A;   #current density(V/m)\n",
+      "rho=E/J;    #resistivity(ohm m)\n",
+      "\n",
+      "#Result\n",
+      "print \"current density is\",round(J/10**6,3),\"*10**6 V/m\"\n",
+      "print \"resistivity is\",round(rho*10**6,2),\"*10**-6 ohm m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "current density is 3.144 *10**6 V/m\n",
+        "resistivity is 1.59 *10**-6 ohm m\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.3, Page number 245"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "n=1;\n",
+      "a=4*10**-10;   #lattice parameter(m)\n",
+      "N=1.56*10**28;  \n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "tow=10**-15;    #collision time(s)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "N=n/(a**3);    #number of electrons per unit volume(per m**3)\n",
+      "sigma=N*e**2*tow/m;   #conductivity(per ohm m)\n",
+      "rho=1/sigma;   #resistivity(ohm m)\n",
+      "\n",
+      "#Result\n",
+      "print \"conductivity is\",round(sigma/10**6,2),\"*10**6 ohm m\"\n",
+      "print \"resistivity is\",rho,\"ohm m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "conductivity is 0.44 *10**6 ohm m\n",
+        "resistivity is 2.275e-06 ohm m\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.4, Page number 247"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "NA=6.02*10**26;   #avagadro number(k/mole)\n",
+      "T=300;     #temperature(K)\n",
+      "EF=2;   #fermi energy(eV)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "C=math.pi**2*k**2*NA*T/(2*EF*e);    #electronic specific heat(J/kmol/K)\n",
+      "\n",
+      "#Result\n",
+      "print \"electronic specific heat is\",int(C),\"J/kmol/K\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "electronic specific heat is 530 J/kmol/K\n"
+       ]
+      }
+     ],
+     "prompt_number": 10
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.5, Page number 247"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "K=327;    #thermal conductivity(W/mK)\n",
+      "T=300;   #temperature(K)\n",
+      "rho=7.13*10**3;    #density(kg/m**3)\n",
+      "NA=6.02*10**26;   #avagadro number(k/mole)\n",
+      "w=65.38;   #atomic weight\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "tow=2.5*10**-14;   #relaxation time(s)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "N=2*rho*NA/w;     #number of electrons per unit volume(per m**3)\n",
+      "sigma=N*e**2*tow/m;   #conductivity(per ohm m)\n",
+      "L=K/(sigma*T);    #lorentz number(W ohm/K**2)\n",
+      "\n",
+      "#Result\n",
+      "print \"lorentz number is\",round(L*10**8,4),\"*10**-8 W ohm/K**2\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "lorentz number is 1.1804 *10**-8 W ohm/K**2\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 12.6, Page number 248"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "n=5*10**28;    #number of atoms(/m**3)\n",
+      "\n",
+      "#Calculation\n",
+      "RH=-1/(n*e);    #hall coefficient(m**3/C)\n",
+      "\n",
+      "#Result\n",
+      "print \"hall coefficient is\",round(RH*10**9,3),\"*10**-9 m**3/C\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "hall coefficient is -0.125 *10**-9 m**3/C\n"
+       ]
+      }
+     ],
+     "prompt_number": 14
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter13.ipynb b/Modern_Physics_By_G.Aruldas/Chapter13.ipynb
new file mode 100755
index 00000000..70f718e0
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter13.ipynb
@@ -0,0 +1,250 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:1e02413599230fcf3193c09944545ea5772a7d8e9a89055fec5a43dcb6e7435b"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "13: Magnetic properties of solids"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.1, Page number 256"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "chi=-4.2*10**-6;    #magnetic susceptibility\n",
+      "H=1.2*10**5;    #magnetic field(A/m)\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "\n",
+      "#Calculation\n",
+      "M=chi*H;    #magnetisation(A/m)\n",
+      "B=mew0*(H+M);   #flux density(T)\n",
+      "mewr=(M/H)+1;   #relative permeability\n",
+      "\n",
+      "#Result\n",
+      "print \"magnetisation is\",M,\"A/m\"\n",
+      "print \"flux density is\",round(B,3),\"T\"\n",
+      "print \"relative permeability is\",round(mewr,6)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "magnetisation is -0.504 A/m\n",
+        "flux density is 0.151 T\n",
+        "relative permeability is 0.999996\n"
+       ]
+      }
+     ],
+     "prompt_number": 4
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.2, Page number 258"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "Z=2;   #atomic number\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "N=28*10**26;   #number of atoms(per m**3)\n",
+      "r=0.6*10**-10;   #mean radius(m)\n",
+      "\n",
+      "#Calculation\n",
+      "chi=-mew0*Z*e**2*N*r**2/(6*m);   #diamagnetic susceptibility\n",
+      "\n",
+      "#Result\n",
+      "print \"diamagnetic susceptibility is\",round(chi*10**8,3),\"*10**-8\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "diamagnetic susceptibility is -11.878 *10**-8\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.3, Page number 259"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "n=2;\n",
+      "a=2.55*10**-10;   #lattice constant(m)\n",
+      "chi=5.6*10**-6;   #susceptibility\n",
+      "Z=1;\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "N=n/(a**3);    #number of electrons per unit volume(per m**3)\n",
+      "rbar=math.sqrt(chi*6*m/(mew0*Z*e**2*N));    #radius of atom(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"radius of atom is\",round(rbar*10**10,3),\"angstrom\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "radius of atom is 0.888 angstrom\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.4, Page number 260"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "T=300;     #temperature(K)\n",
+      "N=6.5*10**25;   #number of atoms(per m**3)\n",
+      "mew=9.27*10**-24;    \n",
+      "\n",
+      "#Calculation\n",
+      "chi=mew0*N*mew**2/(3*k*T);    #susceptibility\n",
+      "\n",
+      "#Result\n",
+      "print \"susceptibility is\",round(chi*10**7,2),\"*10**-7\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "susceptibility is 5.65 *10**-7\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.5, Page number 260"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "rho=4370;    #density(kg/m**3)\n",
+      "NA=6.02*10**26;   #avagadro number(k/mole)\n",
+      "M=168.5;    #molecular weight(kg/kmol)\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "T=300;     #temperature(K)\n",
+      "H=2*10**5;   #electric field(A/m)\n",
+      "mew=2*9.27*10**-24; \n",
+      "\n",
+      "#Calculation\n",
+      "N=rho*NA/M;   \n",
+      "chi=mew0*N*mew**2/(3*k*T);    #susceptibility\n",
+      "M=chi*H;   #magnetisation(A/m)\n",
+      "\n",
+      "#Result\n",
+      "print \"susceptibility is\",round(chi*10**4,4),\"*10**-4\"\n",
+      "print \"magnetisation is\",round(M,3),\"A/m\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "susceptibility is 5.4298 *10**-4\n",
+        "magnetisation is 108.596 A/m\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 17
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter13_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter13_1.ipynb
new file mode 100755
index 00000000..70f718e0
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter13_1.ipynb
@@ -0,0 +1,250 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:1e02413599230fcf3193c09944545ea5772a7d8e9a89055fec5a43dcb6e7435b"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "13: Magnetic properties of solids"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.1, Page number 256"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "chi=-4.2*10**-6;    #magnetic susceptibility\n",
+      "H=1.2*10**5;    #magnetic field(A/m)\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "\n",
+      "#Calculation\n",
+      "M=chi*H;    #magnetisation(A/m)\n",
+      "B=mew0*(H+M);   #flux density(T)\n",
+      "mewr=(M/H)+1;   #relative permeability\n",
+      "\n",
+      "#Result\n",
+      "print \"magnetisation is\",M,\"A/m\"\n",
+      "print \"flux density is\",round(B,3),\"T\"\n",
+      "print \"relative permeability is\",round(mewr,6)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "magnetisation is -0.504 A/m\n",
+        "flux density is 0.151 T\n",
+        "relative permeability is 0.999996\n"
+       ]
+      }
+     ],
+     "prompt_number": 4
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.2, Page number 258"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "Z=2;   #atomic number\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "N=28*10**26;   #number of atoms(per m**3)\n",
+      "r=0.6*10**-10;   #mean radius(m)\n",
+      "\n",
+      "#Calculation\n",
+      "chi=-mew0*Z*e**2*N*r**2/(6*m);   #diamagnetic susceptibility\n",
+      "\n",
+      "#Result\n",
+      "print \"diamagnetic susceptibility is\",round(chi*10**8,3),\"*10**-8\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "diamagnetic susceptibility is -11.878 *10**-8\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.3, Page number 259"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "n=2;\n",
+      "a=2.55*10**-10;   #lattice constant(m)\n",
+      "chi=5.6*10**-6;   #susceptibility\n",
+      "Z=1;\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "N=n/(a**3);    #number of electrons per unit volume(per m**3)\n",
+      "rbar=math.sqrt(chi*6*m/(mew0*Z*e**2*N));    #radius of atom(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"radius of atom is\",round(rbar*10**10,3),\"angstrom\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "radius of atom is 0.888 angstrom\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.4, Page number 260"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "T=300;     #temperature(K)\n",
+      "N=6.5*10**25;   #number of atoms(per m**3)\n",
+      "mew=9.27*10**-24;    \n",
+      "\n",
+      "#Calculation\n",
+      "chi=mew0*N*mew**2/(3*k*T);    #susceptibility\n",
+      "\n",
+      "#Result\n",
+      "print \"susceptibility is\",round(chi*10**7,2),\"*10**-7\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "susceptibility is 5.65 *10**-7\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.5, Page number 260"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "rho=4370;    #density(kg/m**3)\n",
+      "NA=6.02*10**26;   #avagadro number(k/mole)\n",
+      "M=168.5;    #molecular weight(kg/kmol)\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "T=300;     #temperature(K)\n",
+      "H=2*10**5;   #electric field(A/m)\n",
+      "mew=2*9.27*10**-24; \n",
+      "\n",
+      "#Calculation\n",
+      "N=rho*NA/M;   \n",
+      "chi=mew0*N*mew**2/(3*k*T);    #susceptibility\n",
+      "M=chi*H;   #magnetisation(A/m)\n",
+      "\n",
+      "#Result\n",
+      "print \"susceptibility is\",round(chi*10**4,4),\"*10**-4\"\n",
+      "print \"magnetisation is\",round(M,3),\"A/m\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "susceptibility is 5.4298 *10**-4\n",
+        "magnetisation is 108.596 A/m\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 17
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter13_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter13_2.ipynb
new file mode 100755
index 00000000..70f718e0
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter13_2.ipynb
@@ -0,0 +1,250 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:1e02413599230fcf3193c09944545ea5772a7d8e9a89055fec5a43dcb6e7435b"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "13: Magnetic properties of solids"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.1, Page number 256"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "chi=-4.2*10**-6;    #magnetic susceptibility\n",
+      "H=1.2*10**5;    #magnetic field(A/m)\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "\n",
+      "#Calculation\n",
+      "M=chi*H;    #magnetisation(A/m)\n",
+      "B=mew0*(H+M);   #flux density(T)\n",
+      "mewr=(M/H)+1;   #relative permeability\n",
+      "\n",
+      "#Result\n",
+      "print \"magnetisation is\",M,\"A/m\"\n",
+      "print \"flux density is\",round(B,3),\"T\"\n",
+      "print \"relative permeability is\",round(mewr,6)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "magnetisation is -0.504 A/m\n",
+        "flux density is 0.151 T\n",
+        "relative permeability is 0.999996\n"
+       ]
+      }
+     ],
+     "prompt_number": 4
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.2, Page number 258"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "Z=2;   #atomic number\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "N=28*10**26;   #number of atoms(per m**3)\n",
+      "r=0.6*10**-10;   #mean radius(m)\n",
+      "\n",
+      "#Calculation\n",
+      "chi=-mew0*Z*e**2*N*r**2/(6*m);   #diamagnetic susceptibility\n",
+      "\n",
+      "#Result\n",
+      "print \"diamagnetic susceptibility is\",round(chi*10**8,3),\"*10**-8\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "diamagnetic susceptibility is -11.878 *10**-8\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.3, Page number 259"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "n=2;\n",
+      "a=2.55*10**-10;   #lattice constant(m)\n",
+      "chi=5.6*10**-6;   #susceptibility\n",
+      "Z=1;\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "N=n/(a**3);    #number of electrons per unit volume(per m**3)\n",
+      "rbar=math.sqrt(chi*6*m/(mew0*Z*e**2*N));    #radius of atom(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"radius of atom is\",round(rbar*10**10,3),\"angstrom\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "radius of atom is 0.888 angstrom\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.4, Page number 260"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "T=300;     #temperature(K)\n",
+      "N=6.5*10**25;   #number of atoms(per m**3)\n",
+      "mew=9.27*10**-24;    \n",
+      "\n",
+      "#Calculation\n",
+      "chi=mew0*N*mew**2/(3*k*T);    #susceptibility\n",
+      "\n",
+      "#Result\n",
+      "print \"susceptibility is\",round(chi*10**7,2),\"*10**-7\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "susceptibility is 5.65 *10**-7\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.5, Page number 260"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "rho=4370;    #density(kg/m**3)\n",
+      "NA=6.02*10**26;   #avagadro number(k/mole)\n",
+      "M=168.5;    #molecular weight(kg/kmol)\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "T=300;     #temperature(K)\n",
+      "H=2*10**5;   #electric field(A/m)\n",
+      "mew=2*9.27*10**-24; \n",
+      "\n",
+      "#Calculation\n",
+      "N=rho*NA/M;   \n",
+      "chi=mew0*N*mew**2/(3*k*T);    #susceptibility\n",
+      "M=chi*H;   #magnetisation(A/m)\n",
+      "\n",
+      "#Result\n",
+      "print \"susceptibility is\",round(chi*10**4,4),\"*10**-4\"\n",
+      "print \"magnetisation is\",round(M,3),\"A/m\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "susceptibility is 5.4298 *10**-4\n",
+        "magnetisation is 108.596 A/m\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 17
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter13_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter13_3.ipynb
new file mode 100755
index 00000000..70f718e0
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter13_3.ipynb
@@ -0,0 +1,250 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:1e02413599230fcf3193c09944545ea5772a7d8e9a89055fec5a43dcb6e7435b"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "13: Magnetic properties of solids"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.1, Page number 256"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "chi=-4.2*10**-6;    #magnetic susceptibility\n",
+      "H=1.2*10**5;    #magnetic field(A/m)\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "\n",
+      "#Calculation\n",
+      "M=chi*H;    #magnetisation(A/m)\n",
+      "B=mew0*(H+M);   #flux density(T)\n",
+      "mewr=(M/H)+1;   #relative permeability\n",
+      "\n",
+      "#Result\n",
+      "print \"magnetisation is\",M,\"A/m\"\n",
+      "print \"flux density is\",round(B,3),\"T\"\n",
+      "print \"relative permeability is\",round(mewr,6)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "magnetisation is -0.504 A/m\n",
+        "flux density is 0.151 T\n",
+        "relative permeability is 0.999996\n"
+       ]
+      }
+     ],
+     "prompt_number": 4
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.2, Page number 258"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "Z=2;   #atomic number\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "N=28*10**26;   #number of atoms(per m**3)\n",
+      "r=0.6*10**-10;   #mean radius(m)\n",
+      "\n",
+      "#Calculation\n",
+      "chi=-mew0*Z*e**2*N*r**2/(6*m);   #diamagnetic susceptibility\n",
+      "\n",
+      "#Result\n",
+      "print \"diamagnetic susceptibility is\",round(chi*10**8,3),\"*10**-8\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "diamagnetic susceptibility is -11.878 *10**-8\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.3, Page number 259"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "n=2;\n",
+      "a=2.55*10**-10;   #lattice constant(m)\n",
+      "chi=5.6*10**-6;   #susceptibility\n",
+      "Z=1;\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "N=n/(a**3);    #number of electrons per unit volume(per m**3)\n",
+      "rbar=math.sqrt(chi*6*m/(mew0*Z*e**2*N));    #radius of atom(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"radius of atom is\",round(rbar*10**10,3),\"angstrom\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "radius of atom is 0.888 angstrom\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.4, Page number 260"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "T=300;     #temperature(K)\n",
+      "N=6.5*10**25;   #number of atoms(per m**3)\n",
+      "mew=9.27*10**-24;    \n",
+      "\n",
+      "#Calculation\n",
+      "chi=mew0*N*mew**2/(3*k*T);    #susceptibility\n",
+      "\n",
+      "#Result\n",
+      "print \"susceptibility is\",round(chi*10**7,2),\"*10**-7\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "susceptibility is 5.65 *10**-7\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 13.5, Page number 260"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "rho=4370;    #density(kg/m**3)\n",
+      "NA=6.02*10**26;   #avagadro number(k/mole)\n",
+      "M=168.5;    #molecular weight(kg/kmol)\n",
+      "mew0=4*math.pi*10**-7;   #permitivity of free space(H/m)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "T=300;     #temperature(K)\n",
+      "H=2*10**5;   #electric field(A/m)\n",
+      "mew=2*9.27*10**-24; \n",
+      "\n",
+      "#Calculation\n",
+      "N=rho*NA/M;   \n",
+      "chi=mew0*N*mew**2/(3*k*T);    #susceptibility\n",
+      "M=chi*H;   #magnetisation(A/m)\n",
+      "\n",
+      "#Result\n",
+      "print \"susceptibility is\",round(chi*10**4,4),\"*10**-4\"\n",
+      "print \"magnetisation is\",round(M,3),\"A/m\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "susceptibility is 5.4298 *10**-4\n",
+        "magnetisation is 108.596 A/m\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 17
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter14.ipynb b/Modern_Physics_By_G.Aruldas/Chapter14.ipynb
new file mode 100755
index 00000000..b2beeab9
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter14.ipynb
@@ -0,0 +1,107 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:f383b09bed78232b6f6bef91df71b6fd8febd00a3f89287a33c756d53748eb03"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "14: Superconductivity"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 14.1, Page number 272"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "Bc0=0.0305;    #critical field(T)\n",
+      "T=2;   #temperature(K)\n",
+      "Tc=3.722;   #critical temperature(K)\n",
+      "r=2*10**-3;  #diameter(m)\n",
+      "mew0=4*math.pi*10**-7;   #magnetic permeability\n",
+      "\n",
+      "#Calculation\n",
+      "BcT=Bc0*(1-(T/Tc)**2);   #critical field(T)\n",
+      "Ic=2*math.pi*r*BcT/mew0;   #current(A)\n",
+      "\n",
+      "#Result\n",
+      "print \"current is\",round(Ic,1),\"A\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "current is 216.9 A\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 14.2, Page number 274"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "lamda0=37;   #london penetration depth(nm)\n",
+      "T=5.2;    #temperature(K)\n",
+      "Tc=7.193;   #critical temperature(K)\n",
+      "\n",
+      "#Calculation\n",
+      "a=1-(T/Tc)**4;\n",
+      "lamdaT=lamda0*(a**(-1/2));   #penetration depth of lead(nm)\n",
+      "\n",
+      "#Result\n",
+      "print \"penetration depth of lead is\",round(lamdaT,3),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "penetration depth of lead is 43.398 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter14_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter14_1.ipynb
new file mode 100755
index 00000000..b2beeab9
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter14_1.ipynb
@@ -0,0 +1,107 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:f383b09bed78232b6f6bef91df71b6fd8febd00a3f89287a33c756d53748eb03"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "14: Superconductivity"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 14.1, Page number 272"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "Bc0=0.0305;    #critical field(T)\n",
+      "T=2;   #temperature(K)\n",
+      "Tc=3.722;   #critical temperature(K)\n",
+      "r=2*10**-3;  #diameter(m)\n",
+      "mew0=4*math.pi*10**-7;   #magnetic permeability\n",
+      "\n",
+      "#Calculation\n",
+      "BcT=Bc0*(1-(T/Tc)**2);   #critical field(T)\n",
+      "Ic=2*math.pi*r*BcT/mew0;   #current(A)\n",
+      "\n",
+      "#Result\n",
+      "print \"current is\",round(Ic,1),\"A\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "current is 216.9 A\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 14.2, Page number 274"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "lamda0=37;   #london penetration depth(nm)\n",
+      "T=5.2;    #temperature(K)\n",
+      "Tc=7.193;   #critical temperature(K)\n",
+      "\n",
+      "#Calculation\n",
+      "a=1-(T/Tc)**4;\n",
+      "lamdaT=lamda0*(a**(-1/2));   #penetration depth of lead(nm)\n",
+      "\n",
+      "#Result\n",
+      "print \"penetration depth of lead is\",round(lamdaT,3),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "penetration depth of lead is 43.398 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter14_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter14_2.ipynb
new file mode 100755
index 00000000..b2beeab9
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter14_2.ipynb
@@ -0,0 +1,107 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:f383b09bed78232b6f6bef91df71b6fd8febd00a3f89287a33c756d53748eb03"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "14: Superconductivity"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 14.1, Page number 272"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "Bc0=0.0305;    #critical field(T)\n",
+      "T=2;   #temperature(K)\n",
+      "Tc=3.722;   #critical temperature(K)\n",
+      "r=2*10**-3;  #diameter(m)\n",
+      "mew0=4*math.pi*10**-7;   #magnetic permeability\n",
+      "\n",
+      "#Calculation\n",
+      "BcT=Bc0*(1-(T/Tc)**2);   #critical field(T)\n",
+      "Ic=2*math.pi*r*BcT/mew0;   #current(A)\n",
+      "\n",
+      "#Result\n",
+      "print \"current is\",round(Ic,1),\"A\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "current is 216.9 A\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 14.2, Page number 274"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "lamda0=37;   #london penetration depth(nm)\n",
+      "T=5.2;    #temperature(K)\n",
+      "Tc=7.193;   #critical temperature(K)\n",
+      "\n",
+      "#Calculation\n",
+      "a=1-(T/Tc)**4;\n",
+      "lamdaT=lamda0*(a**(-1/2));   #penetration depth of lead(nm)\n",
+      "\n",
+      "#Result\n",
+      "print \"penetration depth of lead is\",round(lamdaT,3),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "penetration depth of lead is 43.398 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter14_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter14_3.ipynb
new file mode 100755
index 00000000..b2beeab9
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter14_3.ipynb
@@ -0,0 +1,107 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:f383b09bed78232b6f6bef91df71b6fd8febd00a3f89287a33c756d53748eb03"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "14: Superconductivity"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 14.1, Page number 272"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "Bc0=0.0305;    #critical field(T)\n",
+      "T=2;   #temperature(K)\n",
+      "Tc=3.722;   #critical temperature(K)\n",
+      "r=2*10**-3;  #diameter(m)\n",
+      "mew0=4*math.pi*10**-7;   #magnetic permeability\n",
+      "\n",
+      "#Calculation\n",
+      "BcT=Bc0*(1-(T/Tc)**2);   #critical field(T)\n",
+      "Ic=2*math.pi*r*BcT/mew0;   #current(A)\n",
+      "\n",
+      "#Result\n",
+      "print \"current is\",round(Ic,1),\"A\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "current is 216.9 A\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 14.2, Page number 274"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "lamda0=37;   #london penetration depth(nm)\n",
+      "T=5.2;    #temperature(K)\n",
+      "Tc=7.193;   #critical temperature(K)\n",
+      "\n",
+      "#Calculation\n",
+      "a=1-(T/Tc)**4;\n",
+      "lamdaT=lamda0*(a**(-1/2));   #penetration depth of lead(nm)\n",
+      "\n",
+      "#Result\n",
+      "print \"penetration depth of lead is\",round(lamdaT,3),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "penetration depth of lead is 43.398 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter15.ipynb b/Modern_Physics_By_G.Aruldas/Chapter15.ipynb
new file mode 100755
index 00000000..48af1473
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter15.ipynb
@@ -0,0 +1,203 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:ede2b0bb266c67744fbe14f69a09ec9b5592c13400e7d0bf2db5fa598ebe9db1"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "15: Lasers"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 15.1, Page number 283"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "T=1000;    #temperature(K)\n",
+      "new1=7.5*10**14;  \n",
+      "new2=4.3*10**14;\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "\n",
+      "#Calculation\n",
+      "kT=k*T;\n",
+      "#optical region extends from 4000 to 7000 angstrom\n",
+      "hnew=h*(new1-new2);  \n",
+      "\n",
+      "#Result\n",
+      "print \"value of kT is\",kT,\"J\"\n",
+      "print \"value of hnew is\",hnew,\"J\"\n",
+      "print \"hnew>kT.therefore spontaneous transitions are dominant ones in optical region\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "value of kT is 1.38e-20 J\n",
+        "value of hnew is 2.12032e-19 J\n",
+        "hnew>kT.therefore spontaneous transitions are dominant ones in optical region\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 15.2, Page number 298"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "P=0.6;   #power(watt)\n",
+      "T=30*10**-3;    #time(s)\n",
+      "lamda=640*10**-9;   #wavelength(m)\n",
+      "\n",
+      "#Calculation\n",
+      "E=P*T;    #energy deposited(J)\n",
+      "n=E*lamda/(h*c);   #number of photons in each pulse\n",
+      "\n",
+      "#Result\n",
+      "print \"energy deposited is\",E,\"J\"\n",
+      "print \"number of photons in each pulse is\",round(n/10**16,1),\"*10**16\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy deposited is 0.018 J\n",
+        "number of photons in each pulse is 5.8 *10**16\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 15.3, Page number 298"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "lamda=5000*10**-10;   #wavelength(m)\n",
+      "f=0.2;   #focal length(m)\n",
+      "a=0.009;   #radius of aperture(m)\n",
+      "P=2.5*10**-3;   #power(W)\n",
+      "\n",
+      "#Calculation\n",
+      "A=math.pi*lamda**2*f**2/a**2;    #area of spot at focal plane(m**2)\n",
+      "I=P/A;   #intensity at focus(W/m**2)\n",
+      "\n",
+      "#Result\n",
+      "print \"area of spot at focal plane is\",round(A*10**10,2),\"*10**-10 m**2\"\n",
+      "print \"intensity at focus is\",round(I/10**6,3),\"*10**6 W/m**2\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "area of spot at focal plane is 3.88 *10**-10 m**2\n",
+        "intensity at focus is 6.446 *10**6 W/m**2\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 15.4, Page number 298"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "lamda=693*10**-9;   #wavelength(m)\n",
+      "D=3*10**-3;    #diameter of mirror(m)\n",
+      "d=300*10**3;   #distance from earth(m)\n",
+      "\n",
+      "#Calculation\n",
+      "delta_theta=1.22*lamda/D;    #angular spread(rad)\n",
+      "a=delta_theta*d;    #diameter of beam on satellite(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"angular spread is\",round(delta_theta*10**4,2),\"*10**-4 rad\"\n",
+      "print \"diameter of beam on satellite is\",round(a,2),\"m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "angular spread is 2.82 *10**-4 rad\n",
+        "diameter of beam on satellite is 84.55 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 15
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter15_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter15_1.ipynb
new file mode 100755
index 00000000..48af1473
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter15_1.ipynb
@@ -0,0 +1,203 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:ede2b0bb266c67744fbe14f69a09ec9b5592c13400e7d0bf2db5fa598ebe9db1"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "15: Lasers"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 15.1, Page number 283"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "T=1000;    #temperature(K)\n",
+      "new1=7.5*10**14;  \n",
+      "new2=4.3*10**14;\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "\n",
+      "#Calculation\n",
+      "kT=k*T;\n",
+      "#optical region extends from 4000 to 7000 angstrom\n",
+      "hnew=h*(new1-new2);  \n",
+      "\n",
+      "#Result\n",
+      "print \"value of kT is\",kT,\"J\"\n",
+      "print \"value of hnew is\",hnew,\"J\"\n",
+      "print \"hnew>kT.therefore spontaneous transitions are dominant ones in optical region\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "value of kT is 1.38e-20 J\n",
+        "value of hnew is 2.12032e-19 J\n",
+        "hnew>kT.therefore spontaneous transitions are dominant ones in optical region\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 15.2, Page number 298"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "P=0.6;   #power(watt)\n",
+      "T=30*10**-3;    #time(s)\n",
+      "lamda=640*10**-9;   #wavelength(m)\n",
+      "\n",
+      "#Calculation\n",
+      "E=P*T;    #energy deposited(J)\n",
+      "n=E*lamda/(h*c);   #number of photons in each pulse\n",
+      "\n",
+      "#Result\n",
+      "print \"energy deposited is\",E,\"J\"\n",
+      "print \"number of photons in each pulse is\",round(n/10**16,1),\"*10**16\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy deposited is 0.018 J\n",
+        "number of photons in each pulse is 5.8 *10**16\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 15.3, Page number 298"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "lamda=5000*10**-10;   #wavelength(m)\n",
+      "f=0.2;   #focal length(m)\n",
+      "a=0.009;   #radius of aperture(m)\n",
+      "P=2.5*10**-3;   #power(W)\n",
+      "\n",
+      "#Calculation\n",
+      "A=math.pi*lamda**2*f**2/a**2;    #area of spot at focal plane(m**2)\n",
+      "I=P/A;   #intensity at focus(W/m**2)\n",
+      "\n",
+      "#Result\n",
+      "print \"area of spot at focal plane is\",round(A*10**10,2),\"*10**-10 m**2\"\n",
+      "print \"intensity at focus is\",round(I/10**6,3),\"*10**6 W/m**2\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "area of spot at focal plane is 3.88 *10**-10 m**2\n",
+        "intensity at focus is 6.446 *10**6 W/m**2\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 15.4, Page number 298"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "lamda=693*10**-9;   #wavelength(m)\n",
+      "D=3*10**-3;    #diameter of mirror(m)\n",
+      "d=300*10**3;   #distance from earth(m)\n",
+      "\n",
+      "#Calculation\n",
+      "delta_theta=1.22*lamda/D;    #angular spread(rad)\n",
+      "a=delta_theta*d;    #diameter of beam on satellite(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"angular spread is\",round(delta_theta*10**4,2),\"*10**-4 rad\"\n",
+      "print \"diameter of beam on satellite is\",round(a,2),\"m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "angular spread is 2.82 *10**-4 rad\n",
+        "diameter of beam on satellite is 84.55 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 15
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter15_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter15_2.ipynb
new file mode 100755
index 00000000..48af1473
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter15_2.ipynb
@@ -0,0 +1,203 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:ede2b0bb266c67744fbe14f69a09ec9b5592c13400e7d0bf2db5fa598ebe9db1"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "15: Lasers"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 15.1, Page number 283"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "T=1000;    #temperature(K)\n",
+      "new1=7.5*10**14;  \n",
+      "new2=4.3*10**14;\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "\n",
+      "#Calculation\n",
+      "kT=k*T;\n",
+      "#optical region extends from 4000 to 7000 angstrom\n",
+      "hnew=h*(new1-new2);  \n",
+      "\n",
+      "#Result\n",
+      "print \"value of kT is\",kT,\"J\"\n",
+      "print \"value of hnew is\",hnew,\"J\"\n",
+      "print \"hnew>kT.therefore spontaneous transitions are dominant ones in optical region\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "value of kT is 1.38e-20 J\n",
+        "value of hnew is 2.12032e-19 J\n",
+        "hnew>kT.therefore spontaneous transitions are dominant ones in optical region\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 15.2, Page number 298"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "P=0.6;   #power(watt)\n",
+      "T=30*10**-3;    #time(s)\n",
+      "lamda=640*10**-9;   #wavelength(m)\n",
+      "\n",
+      "#Calculation\n",
+      "E=P*T;    #energy deposited(J)\n",
+      "n=E*lamda/(h*c);   #number of photons in each pulse\n",
+      "\n",
+      "#Result\n",
+      "print \"energy deposited is\",E,\"J\"\n",
+      "print \"number of photons in each pulse is\",round(n/10**16,1),\"*10**16\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy deposited is 0.018 J\n",
+        "number of photons in each pulse is 5.8 *10**16\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 15.3, Page number 298"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "lamda=5000*10**-10;   #wavelength(m)\n",
+      "f=0.2;   #focal length(m)\n",
+      "a=0.009;   #radius of aperture(m)\n",
+      "P=2.5*10**-3;   #power(W)\n",
+      "\n",
+      "#Calculation\n",
+      "A=math.pi*lamda**2*f**2/a**2;    #area of spot at focal plane(m**2)\n",
+      "I=P/A;   #intensity at focus(W/m**2)\n",
+      "\n",
+      "#Result\n",
+      "print \"area of spot at focal plane is\",round(A*10**10,2),\"*10**-10 m**2\"\n",
+      "print \"intensity at focus is\",round(I/10**6,3),\"*10**6 W/m**2\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "area of spot at focal plane is 3.88 *10**-10 m**2\n",
+        "intensity at focus is 6.446 *10**6 W/m**2\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 15.4, Page number 298"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "lamda=693*10**-9;   #wavelength(m)\n",
+      "D=3*10**-3;    #diameter of mirror(m)\n",
+      "d=300*10**3;   #distance from earth(m)\n",
+      "\n",
+      "#Calculation\n",
+      "delta_theta=1.22*lamda/D;    #angular spread(rad)\n",
+      "a=delta_theta*d;    #diameter of beam on satellite(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"angular spread is\",round(delta_theta*10**4,2),\"*10**-4 rad\"\n",
+      "print \"diameter of beam on satellite is\",round(a,2),\"m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "angular spread is 2.82 *10**-4 rad\n",
+        "diameter of beam on satellite is 84.55 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 15
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter15_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter15_3.ipynb
new file mode 100755
index 00000000..48af1473
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter15_3.ipynb
@@ -0,0 +1,203 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:ede2b0bb266c67744fbe14f69a09ec9b5592c13400e7d0bf2db5fa598ebe9db1"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "15: Lasers"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 15.1, Page number 283"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "T=1000;    #temperature(K)\n",
+      "new1=7.5*10**14;  \n",
+      "new2=4.3*10**14;\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "\n",
+      "#Calculation\n",
+      "kT=k*T;\n",
+      "#optical region extends from 4000 to 7000 angstrom\n",
+      "hnew=h*(new1-new2);  \n",
+      "\n",
+      "#Result\n",
+      "print \"value of kT is\",kT,\"J\"\n",
+      "print \"value of hnew is\",hnew,\"J\"\n",
+      "print \"hnew>kT.therefore spontaneous transitions are dominant ones in optical region\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "value of kT is 1.38e-20 J\n",
+        "value of hnew is 2.12032e-19 J\n",
+        "hnew>kT.therefore spontaneous transitions are dominant ones in optical region\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 15.2, Page number 298"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "P=0.6;   #power(watt)\n",
+      "T=30*10**-3;    #time(s)\n",
+      "lamda=640*10**-9;   #wavelength(m)\n",
+      "\n",
+      "#Calculation\n",
+      "E=P*T;    #energy deposited(J)\n",
+      "n=E*lamda/(h*c);   #number of photons in each pulse\n",
+      "\n",
+      "#Result\n",
+      "print \"energy deposited is\",E,\"J\"\n",
+      "print \"number of photons in each pulse is\",round(n/10**16,1),\"*10**16\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy deposited is 0.018 J\n",
+        "number of photons in each pulse is 5.8 *10**16\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 15.3, Page number 298"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "lamda=5000*10**-10;   #wavelength(m)\n",
+      "f=0.2;   #focal length(m)\n",
+      "a=0.009;   #radius of aperture(m)\n",
+      "P=2.5*10**-3;   #power(W)\n",
+      "\n",
+      "#Calculation\n",
+      "A=math.pi*lamda**2*f**2/a**2;    #area of spot at focal plane(m**2)\n",
+      "I=P/A;   #intensity at focus(W/m**2)\n",
+      "\n",
+      "#Result\n",
+      "print \"area of spot at focal plane is\",round(A*10**10,2),\"*10**-10 m**2\"\n",
+      "print \"intensity at focus is\",round(I/10**6,3),\"*10**6 W/m**2\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "area of spot at focal plane is 3.88 *10**-10 m**2\n",
+        "intensity at focus is 6.446 *10**6 W/m**2\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 15.4, Page number 298"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "lamda=693*10**-9;   #wavelength(m)\n",
+      "D=3*10**-3;    #diameter of mirror(m)\n",
+      "d=300*10**3;   #distance from earth(m)\n",
+      "\n",
+      "#Calculation\n",
+      "delta_theta=1.22*lamda/D;    #angular spread(rad)\n",
+      "a=delta_theta*d;    #diameter of beam on satellite(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"angular spread is\",round(delta_theta*10**4,2),\"*10**-4 rad\"\n",
+      "print \"diameter of beam on satellite is\",round(a,2),\"m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "angular spread is 2.82 *10**-4 rad\n",
+        "diameter of beam on satellite is 84.55 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 15
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter16.ipynb b/Modern_Physics_By_G.Aruldas/Chapter16.ipynb
new file mode 100755
index 00000000..932f4802
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter16.ipynb
@@ -0,0 +1,114 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:8689775b6694dc6c6ea95bc809bbd7280d9553003ec1dbe78844db2dc6fa68f3"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "16: Fibre optics and holography"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 16.1, Page number 306"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "n2=1.4;    #refractive index of cladding\n",
+      "n1=1.43;   #refractive index of core\n",
+      "\n",
+      "#Calculation\n",
+      "costhetac=n2/n1;  \n",
+      "thetac=math.acos(costhetac);     #propagation angle(radian)\n",
+      "thetac=thetac*180/math.pi;    #propagation angle(degrees)\n",
+      "NA=math.sqrt(n1**2-n2**2);   #numerical aperture\n",
+      "thetaa=math.asin(NA);    #angle(radian)\n",
+      "thetaa=thetaa*180/math.pi;    #angle(degrees)\n",
+      "thetaa=2*thetaa;    #acceptance angle(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"propagation angle is\",round(thetac,1),\"degrees\"\n",
+      "print \"numerical aperture is\",round(NA,4)\n",
+      "print \"acceptance angle is\",round(thetaa,2),\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "propagation angle is 11.8 degrees\n",
+        "numerical aperture is 0.2914\n",
+        "acceptance angle is 33.88 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 16.3, Page number 311"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "z=30;    #length of optical fibre(km)\n",
+      "alpha=0.8;    #fibre loss(dB/km)\n",
+      "Pi=200;   #input power(micro W)\n",
+      "\n",
+      "#Calculation\n",
+      "a=alpha*z/10;\n",
+      "b=10**a;\n",
+      "P0=Pi/b;    #output power(micro W)\n",
+      "\n",
+      "#Result\n",
+      "print \"output power is\",round(P0,3),\"micro W\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "output power is 0.796 micro W\n"
+       ]
+      }
+     ],
+     "prompt_number": 10
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter16_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter16_1.ipynb
new file mode 100755
index 00000000..932f4802
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter16_1.ipynb
@@ -0,0 +1,114 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:8689775b6694dc6c6ea95bc809bbd7280d9553003ec1dbe78844db2dc6fa68f3"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "16: Fibre optics and holography"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 16.1, Page number 306"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "n2=1.4;    #refractive index of cladding\n",
+      "n1=1.43;   #refractive index of core\n",
+      "\n",
+      "#Calculation\n",
+      "costhetac=n2/n1;  \n",
+      "thetac=math.acos(costhetac);     #propagation angle(radian)\n",
+      "thetac=thetac*180/math.pi;    #propagation angle(degrees)\n",
+      "NA=math.sqrt(n1**2-n2**2);   #numerical aperture\n",
+      "thetaa=math.asin(NA);    #angle(radian)\n",
+      "thetaa=thetaa*180/math.pi;    #angle(degrees)\n",
+      "thetaa=2*thetaa;    #acceptance angle(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"propagation angle is\",round(thetac,1),\"degrees\"\n",
+      "print \"numerical aperture is\",round(NA,4)\n",
+      "print \"acceptance angle is\",round(thetaa,2),\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "propagation angle is 11.8 degrees\n",
+        "numerical aperture is 0.2914\n",
+        "acceptance angle is 33.88 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 16.3, Page number 311"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "z=30;    #length of optical fibre(km)\n",
+      "alpha=0.8;    #fibre loss(dB/km)\n",
+      "Pi=200;   #input power(micro W)\n",
+      "\n",
+      "#Calculation\n",
+      "a=alpha*z/10;\n",
+      "b=10**a;\n",
+      "P0=Pi/b;    #output power(micro W)\n",
+      "\n",
+      "#Result\n",
+      "print \"output power is\",round(P0,3),\"micro W\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "output power is 0.796 micro W\n"
+       ]
+      }
+     ],
+     "prompt_number": 10
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter16_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter16_2.ipynb
new file mode 100755
index 00000000..932f4802
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter16_2.ipynb
@@ -0,0 +1,114 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:8689775b6694dc6c6ea95bc809bbd7280d9553003ec1dbe78844db2dc6fa68f3"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "16: Fibre optics and holography"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 16.1, Page number 306"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "n2=1.4;    #refractive index of cladding\n",
+      "n1=1.43;   #refractive index of core\n",
+      "\n",
+      "#Calculation\n",
+      "costhetac=n2/n1;  \n",
+      "thetac=math.acos(costhetac);     #propagation angle(radian)\n",
+      "thetac=thetac*180/math.pi;    #propagation angle(degrees)\n",
+      "NA=math.sqrt(n1**2-n2**2);   #numerical aperture\n",
+      "thetaa=math.asin(NA);    #angle(radian)\n",
+      "thetaa=thetaa*180/math.pi;    #angle(degrees)\n",
+      "thetaa=2*thetaa;    #acceptance angle(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"propagation angle is\",round(thetac,1),\"degrees\"\n",
+      "print \"numerical aperture is\",round(NA,4)\n",
+      "print \"acceptance angle is\",round(thetaa,2),\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "propagation angle is 11.8 degrees\n",
+        "numerical aperture is 0.2914\n",
+        "acceptance angle is 33.88 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 16.3, Page number 311"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "z=30;    #length of optical fibre(km)\n",
+      "alpha=0.8;    #fibre loss(dB/km)\n",
+      "Pi=200;   #input power(micro W)\n",
+      "\n",
+      "#Calculation\n",
+      "a=alpha*z/10;\n",
+      "b=10**a;\n",
+      "P0=Pi/b;    #output power(micro W)\n",
+      "\n",
+      "#Result\n",
+      "print \"output power is\",round(P0,3),\"micro W\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "output power is 0.796 micro W\n"
+       ]
+      }
+     ],
+     "prompt_number": 10
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter16_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter16_3.ipynb
new file mode 100755
index 00000000..932f4802
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter16_3.ipynb
@@ -0,0 +1,114 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:8689775b6694dc6c6ea95bc809bbd7280d9553003ec1dbe78844db2dc6fa68f3"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "16: Fibre optics and holography"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 16.1, Page number 306"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "n2=1.4;    #refractive index of cladding\n",
+      "n1=1.43;   #refractive index of core\n",
+      "\n",
+      "#Calculation\n",
+      "costhetac=n2/n1;  \n",
+      "thetac=math.acos(costhetac);     #propagation angle(radian)\n",
+      "thetac=thetac*180/math.pi;    #propagation angle(degrees)\n",
+      "NA=math.sqrt(n1**2-n2**2);   #numerical aperture\n",
+      "thetaa=math.asin(NA);    #angle(radian)\n",
+      "thetaa=thetaa*180/math.pi;    #angle(degrees)\n",
+      "thetaa=2*thetaa;    #acceptance angle(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"propagation angle is\",round(thetac,1),\"degrees\"\n",
+      "print \"numerical aperture is\",round(NA,4)\n",
+      "print \"acceptance angle is\",round(thetaa,2),\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "propagation angle is 11.8 degrees\n",
+        "numerical aperture is 0.2914\n",
+        "acceptance angle is 33.88 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 16.3, Page number 311"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "z=30;    #length of optical fibre(km)\n",
+      "alpha=0.8;    #fibre loss(dB/km)\n",
+      "Pi=200;   #input power(micro W)\n",
+      "\n",
+      "#Calculation\n",
+      "a=alpha*z/10;\n",
+      "b=10**a;\n",
+      "P0=Pi/b;    #output power(micro W)\n",
+      "\n",
+      "#Result\n",
+      "print \"output power is\",round(P0,3),\"micro W\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "output power is 0.796 micro W\n"
+       ]
+      }
+     ],
+     "prompt_number": 10
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter17.ipynb b/Modern_Physics_By_G.Aruldas/Chapter17.ipynb
new file mode 100755
index 00000000..61dae782
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter17.ipynb
@@ -0,0 +1,293 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:d405bf204e77196ade310e0be88ebb97609af7dc21d3bd3e418e5c80ec00e4d3"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "17: Nuclear properties"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.1, Page number 324"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m=1.67*10**-27;    #nucleon mass(kg)\n",
+      "R0=1.2*10**-15;    #radius of nucleus(m)\n",
+      "\n",
+      "#Calculation\n",
+      "d=m*3/(4*math.pi*R0**3);   #density of nucleus(kg/m**3)\n",
+      "\n",
+      "#Result\n",
+      "print \"density of nucleus is\",round(d/10**17,1),\"*10**17 kg/m**3\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "density of nucleus is 2.3 *10**17 kg/m**3\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.2, Page number 324"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "a=1.2*10**-15;\n",
+      "k=9*10**9;   #value of N(Nm**2/C**2)\n",
+      "q1=2;\n",
+      "q2=90;\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "r=a*((4**(1/3))+(228**(1/3)));    #distance(m)\n",
+      "E=k*q1*q2*e**2/r;    #kinetic energy(J)\n",
+      "E=E/(e*10**6);     #kinetic energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"potential energy is 0. kinetic energy is\",round(E,1),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "potential energy is 0. kinetic energy is 28.1 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.3, Page number 326"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "E=2.48*10**4;    #electric field(V/m)\n",
+      "m=1.6605*10**-27;    #nucleon mass(kg)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "B=0.75;    #magnetic field(T)\n",
+      "\n",
+      "#Calculation\n",
+      "r1=E*12*m/(e*B**2);    #distance on photographic plate for 12C(m)\n",
+      "r1=r1*10**3;   #distance on photographic plate for 12C(mm)\n",
+      "r2=E*13*m/(e*B**2);    #distance on photographic plate for 13C(m)\n",
+      "r2=r2*10**3;   #distance on photographic plate for 13C(mm)\n",
+      "r3=E*14*m/(e*B**2);    #distance on photographic plate for 14C(m)\n",
+      "r3=r3*10**3;   #distance on photographic plate for 14C(mm)\n",
+      "r4=(2*r2)-(2*r1);   #distance between lines of 13C and 12C(mm)\n",
+      "r5=(2*r3)-(2*r2);   #distance between lines of 14C and 13C(mm)\n",
+      "r=r4/2;    #distance if ions are doubly charged(mm)\n",
+      "\n",
+      "#Result\n",
+      "print \"distance on photographic plate for 12C is\",round(r1,2),\"mm\"\n",
+      "print \"distance on photographic plate for 13C is\",round(r2,2),\"mm\"\n",
+      "print \"distance on photographic plate for 14C is\",round(r3,2),\"mm\"\n",
+      "print \"distance if ions are doubly charged is\",round(r,2),\"mm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "distance on photographic plate for 12C is 5.49 mm\n",
+        "distance on photographic plate for 13C is 5.95 mm\n",
+        "distance on photographic plate for 14C is 6.41 mm\n",
+        "distance if ions are doubly charged is 0.46 mm\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.4, Page number 327"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "n=6;   #number of neutrons\n",
+      "p=6;   #number of protons\n",
+      "M=12;  #mass of 12C6(u)\n",
+      "E=931.5;  #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "mn=n*1.008665;   #mass of neutrons(u)\n",
+      "mp=p*1.007825;    #mass of hydrogen atoms(u)\n",
+      "m=mp+mn;   #total mass(u)\n",
+      "md=m-M;    #mass deficiency(u)\n",
+      "BE=md*E;   #binding energy(MeV)\n",
+      "be=BE/12;  #average binding energy per nucleon(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"binding energy is\",round(BE,2),\"MeV\"\n",
+      "print \"average binding energy per nucleon is\",round(be,2),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "binding energy is 92.16 MeV\n",
+        "average binding energy per nucleon is 7.68 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.6, Page number 335"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "M22Na=21.9944;   #mass of 22Na(u)\n",
+      "m=1.008665;   #mass of last neutron(u)\n",
+      "M23Na=22.989767;   #mass of 23Na(u)\n",
+      "E=931.5;  #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "M=M22Na+m;   \n",
+      "md=M-M23Na;     #mass deficiency(u)\n",
+      "BE=md*E;    #binding energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"binding energy is\",round(BE,1),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "binding energy is 12.4 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.7, Page number 341"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "hbar=1.05*10**-34;   \n",
+      "c=3*10**8;   #speed of light(m/s)\n",
+      "mpi=140;    #mass of pi-meson(MeV/c**2)\n",
+      "e=1.6*10**-13;\n",
+      "\n",
+      "#Calculation\n",
+      "r=hbar*c/(mpi*e);    #range of nuclear force(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"range of nuclear force is\",round(r*10**15,1),\"fm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "range of nuclear force is 1.4 fm\n"
+       ]
+      }
+     ],
+     "prompt_number": 13
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter17_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter17_1.ipynb
new file mode 100755
index 00000000..61dae782
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter17_1.ipynb
@@ -0,0 +1,293 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:d405bf204e77196ade310e0be88ebb97609af7dc21d3bd3e418e5c80ec00e4d3"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "17: Nuclear properties"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.1, Page number 324"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m=1.67*10**-27;    #nucleon mass(kg)\n",
+      "R0=1.2*10**-15;    #radius of nucleus(m)\n",
+      "\n",
+      "#Calculation\n",
+      "d=m*3/(4*math.pi*R0**3);   #density of nucleus(kg/m**3)\n",
+      "\n",
+      "#Result\n",
+      "print \"density of nucleus is\",round(d/10**17,1),\"*10**17 kg/m**3\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "density of nucleus is 2.3 *10**17 kg/m**3\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.2, Page number 324"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "a=1.2*10**-15;\n",
+      "k=9*10**9;   #value of N(Nm**2/C**2)\n",
+      "q1=2;\n",
+      "q2=90;\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "r=a*((4**(1/3))+(228**(1/3)));    #distance(m)\n",
+      "E=k*q1*q2*e**2/r;    #kinetic energy(J)\n",
+      "E=E/(e*10**6);     #kinetic energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"potential energy is 0. kinetic energy is\",round(E,1),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "potential energy is 0. kinetic energy is 28.1 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.3, Page number 326"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "E=2.48*10**4;    #electric field(V/m)\n",
+      "m=1.6605*10**-27;    #nucleon mass(kg)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "B=0.75;    #magnetic field(T)\n",
+      "\n",
+      "#Calculation\n",
+      "r1=E*12*m/(e*B**2);    #distance on photographic plate for 12C(m)\n",
+      "r1=r1*10**3;   #distance on photographic plate for 12C(mm)\n",
+      "r2=E*13*m/(e*B**2);    #distance on photographic plate for 13C(m)\n",
+      "r2=r2*10**3;   #distance on photographic plate for 13C(mm)\n",
+      "r3=E*14*m/(e*B**2);    #distance on photographic plate for 14C(m)\n",
+      "r3=r3*10**3;   #distance on photographic plate for 14C(mm)\n",
+      "r4=(2*r2)-(2*r1);   #distance between lines of 13C and 12C(mm)\n",
+      "r5=(2*r3)-(2*r2);   #distance between lines of 14C and 13C(mm)\n",
+      "r=r4/2;    #distance if ions are doubly charged(mm)\n",
+      "\n",
+      "#Result\n",
+      "print \"distance on photographic plate for 12C is\",round(r1,2),\"mm\"\n",
+      "print \"distance on photographic plate for 13C is\",round(r2,2),\"mm\"\n",
+      "print \"distance on photographic plate for 14C is\",round(r3,2),\"mm\"\n",
+      "print \"distance if ions are doubly charged is\",round(r,2),\"mm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "distance on photographic plate for 12C is 5.49 mm\n",
+        "distance on photographic plate for 13C is 5.95 mm\n",
+        "distance on photographic plate for 14C is 6.41 mm\n",
+        "distance if ions are doubly charged is 0.46 mm\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.4, Page number 327"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "n=6;   #number of neutrons\n",
+      "p=6;   #number of protons\n",
+      "M=12;  #mass of 12C6(u)\n",
+      "E=931.5;  #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "mn=n*1.008665;   #mass of neutrons(u)\n",
+      "mp=p*1.007825;    #mass of hydrogen atoms(u)\n",
+      "m=mp+mn;   #total mass(u)\n",
+      "md=m-M;    #mass deficiency(u)\n",
+      "BE=md*E;   #binding energy(MeV)\n",
+      "be=BE/12;  #average binding energy per nucleon(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"binding energy is\",round(BE,2),\"MeV\"\n",
+      "print \"average binding energy per nucleon is\",round(be,2),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "binding energy is 92.16 MeV\n",
+        "average binding energy per nucleon is 7.68 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.6, Page number 335"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "M22Na=21.9944;   #mass of 22Na(u)\n",
+      "m=1.008665;   #mass of last neutron(u)\n",
+      "M23Na=22.989767;   #mass of 23Na(u)\n",
+      "E=931.5;  #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "M=M22Na+m;   \n",
+      "md=M-M23Na;     #mass deficiency(u)\n",
+      "BE=md*E;    #binding energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"binding energy is\",round(BE,1),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "binding energy is 12.4 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.7, Page number 341"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "hbar=1.05*10**-34;   \n",
+      "c=3*10**8;   #speed of light(m/s)\n",
+      "mpi=140;    #mass of pi-meson(MeV/c**2)\n",
+      "e=1.6*10**-13;\n",
+      "\n",
+      "#Calculation\n",
+      "r=hbar*c/(mpi*e);    #range of nuclear force(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"range of nuclear force is\",round(r*10**15,1),\"fm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "range of nuclear force is 1.4 fm\n"
+       ]
+      }
+     ],
+     "prompt_number": 13
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter17_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter17_2.ipynb
new file mode 100755
index 00000000..61dae782
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter17_2.ipynb
@@ -0,0 +1,293 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:d405bf204e77196ade310e0be88ebb97609af7dc21d3bd3e418e5c80ec00e4d3"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "17: Nuclear properties"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.1, Page number 324"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m=1.67*10**-27;    #nucleon mass(kg)\n",
+      "R0=1.2*10**-15;    #radius of nucleus(m)\n",
+      "\n",
+      "#Calculation\n",
+      "d=m*3/(4*math.pi*R0**3);   #density of nucleus(kg/m**3)\n",
+      "\n",
+      "#Result\n",
+      "print \"density of nucleus is\",round(d/10**17,1),\"*10**17 kg/m**3\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "density of nucleus is 2.3 *10**17 kg/m**3\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.2, Page number 324"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "a=1.2*10**-15;\n",
+      "k=9*10**9;   #value of N(Nm**2/C**2)\n",
+      "q1=2;\n",
+      "q2=90;\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "r=a*((4**(1/3))+(228**(1/3)));    #distance(m)\n",
+      "E=k*q1*q2*e**2/r;    #kinetic energy(J)\n",
+      "E=E/(e*10**6);     #kinetic energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"potential energy is 0. kinetic energy is\",round(E,1),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "potential energy is 0. kinetic energy is 28.1 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.3, Page number 326"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "E=2.48*10**4;    #electric field(V/m)\n",
+      "m=1.6605*10**-27;    #nucleon mass(kg)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "B=0.75;    #magnetic field(T)\n",
+      "\n",
+      "#Calculation\n",
+      "r1=E*12*m/(e*B**2);    #distance on photographic plate for 12C(m)\n",
+      "r1=r1*10**3;   #distance on photographic plate for 12C(mm)\n",
+      "r2=E*13*m/(e*B**2);    #distance on photographic plate for 13C(m)\n",
+      "r2=r2*10**3;   #distance on photographic plate for 13C(mm)\n",
+      "r3=E*14*m/(e*B**2);    #distance on photographic plate for 14C(m)\n",
+      "r3=r3*10**3;   #distance on photographic plate for 14C(mm)\n",
+      "r4=(2*r2)-(2*r1);   #distance between lines of 13C and 12C(mm)\n",
+      "r5=(2*r3)-(2*r2);   #distance between lines of 14C and 13C(mm)\n",
+      "r=r4/2;    #distance if ions are doubly charged(mm)\n",
+      "\n",
+      "#Result\n",
+      "print \"distance on photographic plate for 12C is\",round(r1,2),\"mm\"\n",
+      "print \"distance on photographic plate for 13C is\",round(r2,2),\"mm\"\n",
+      "print \"distance on photographic plate for 14C is\",round(r3,2),\"mm\"\n",
+      "print \"distance if ions are doubly charged is\",round(r,2),\"mm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "distance on photographic plate for 12C is 5.49 mm\n",
+        "distance on photographic plate for 13C is 5.95 mm\n",
+        "distance on photographic plate for 14C is 6.41 mm\n",
+        "distance if ions are doubly charged is 0.46 mm\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.4, Page number 327"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "n=6;   #number of neutrons\n",
+      "p=6;   #number of protons\n",
+      "M=12;  #mass of 12C6(u)\n",
+      "E=931.5;  #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "mn=n*1.008665;   #mass of neutrons(u)\n",
+      "mp=p*1.007825;    #mass of hydrogen atoms(u)\n",
+      "m=mp+mn;   #total mass(u)\n",
+      "md=m-M;    #mass deficiency(u)\n",
+      "BE=md*E;   #binding energy(MeV)\n",
+      "be=BE/12;  #average binding energy per nucleon(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"binding energy is\",round(BE,2),\"MeV\"\n",
+      "print \"average binding energy per nucleon is\",round(be,2),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "binding energy is 92.16 MeV\n",
+        "average binding energy per nucleon is 7.68 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.6, Page number 335"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "M22Na=21.9944;   #mass of 22Na(u)\n",
+      "m=1.008665;   #mass of last neutron(u)\n",
+      "M23Na=22.989767;   #mass of 23Na(u)\n",
+      "E=931.5;  #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "M=M22Na+m;   \n",
+      "md=M-M23Na;     #mass deficiency(u)\n",
+      "BE=md*E;    #binding energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"binding energy is\",round(BE,1),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "binding energy is 12.4 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.7, Page number 341"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "hbar=1.05*10**-34;   \n",
+      "c=3*10**8;   #speed of light(m/s)\n",
+      "mpi=140;    #mass of pi-meson(MeV/c**2)\n",
+      "e=1.6*10**-13;\n",
+      "\n",
+      "#Calculation\n",
+      "r=hbar*c/(mpi*e);    #range of nuclear force(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"range of nuclear force is\",round(r*10**15,1),\"fm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "range of nuclear force is 1.4 fm\n"
+       ]
+      }
+     ],
+     "prompt_number": 13
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter17_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter17_3.ipynb
new file mode 100755
index 00000000..61dae782
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter17_3.ipynb
@@ -0,0 +1,293 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:d405bf204e77196ade310e0be88ebb97609af7dc21d3bd3e418e5c80ec00e4d3"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "17: Nuclear properties"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.1, Page number 324"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m=1.67*10**-27;    #nucleon mass(kg)\n",
+      "R0=1.2*10**-15;    #radius of nucleus(m)\n",
+      "\n",
+      "#Calculation\n",
+      "d=m*3/(4*math.pi*R0**3);   #density of nucleus(kg/m**3)\n",
+      "\n",
+      "#Result\n",
+      "print \"density of nucleus is\",round(d/10**17,1),\"*10**17 kg/m**3\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "density of nucleus is 2.3 *10**17 kg/m**3\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.2, Page number 324"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "a=1.2*10**-15;\n",
+      "k=9*10**9;   #value of N(Nm**2/C**2)\n",
+      "q1=2;\n",
+      "q2=90;\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "r=a*((4**(1/3))+(228**(1/3)));    #distance(m)\n",
+      "E=k*q1*q2*e**2/r;    #kinetic energy(J)\n",
+      "E=E/(e*10**6);     #kinetic energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"potential energy is 0. kinetic energy is\",round(E,1),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "potential energy is 0. kinetic energy is 28.1 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.3, Page number 326"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "E=2.48*10**4;    #electric field(V/m)\n",
+      "m=1.6605*10**-27;    #nucleon mass(kg)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "B=0.75;    #magnetic field(T)\n",
+      "\n",
+      "#Calculation\n",
+      "r1=E*12*m/(e*B**2);    #distance on photographic plate for 12C(m)\n",
+      "r1=r1*10**3;   #distance on photographic plate for 12C(mm)\n",
+      "r2=E*13*m/(e*B**2);    #distance on photographic plate for 13C(m)\n",
+      "r2=r2*10**3;   #distance on photographic plate for 13C(mm)\n",
+      "r3=E*14*m/(e*B**2);    #distance on photographic plate for 14C(m)\n",
+      "r3=r3*10**3;   #distance on photographic plate for 14C(mm)\n",
+      "r4=(2*r2)-(2*r1);   #distance between lines of 13C and 12C(mm)\n",
+      "r5=(2*r3)-(2*r2);   #distance between lines of 14C and 13C(mm)\n",
+      "r=r4/2;    #distance if ions are doubly charged(mm)\n",
+      "\n",
+      "#Result\n",
+      "print \"distance on photographic plate for 12C is\",round(r1,2),\"mm\"\n",
+      "print \"distance on photographic plate for 13C is\",round(r2,2),\"mm\"\n",
+      "print \"distance on photographic plate for 14C is\",round(r3,2),\"mm\"\n",
+      "print \"distance if ions are doubly charged is\",round(r,2),\"mm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "distance on photographic plate for 12C is 5.49 mm\n",
+        "distance on photographic plate for 13C is 5.95 mm\n",
+        "distance on photographic plate for 14C is 6.41 mm\n",
+        "distance if ions are doubly charged is 0.46 mm\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.4, Page number 327"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "n=6;   #number of neutrons\n",
+      "p=6;   #number of protons\n",
+      "M=12;  #mass of 12C6(u)\n",
+      "E=931.5;  #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "mn=n*1.008665;   #mass of neutrons(u)\n",
+      "mp=p*1.007825;    #mass of hydrogen atoms(u)\n",
+      "m=mp+mn;   #total mass(u)\n",
+      "md=m-M;    #mass deficiency(u)\n",
+      "BE=md*E;   #binding energy(MeV)\n",
+      "be=BE/12;  #average binding energy per nucleon(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"binding energy is\",round(BE,2),\"MeV\"\n",
+      "print \"average binding energy per nucleon is\",round(be,2),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "binding energy is 92.16 MeV\n",
+        "average binding energy per nucleon is 7.68 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.6, Page number 335"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "M22Na=21.9944;   #mass of 22Na(u)\n",
+      "m=1.008665;   #mass of last neutron(u)\n",
+      "M23Na=22.989767;   #mass of 23Na(u)\n",
+      "E=931.5;  #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "M=M22Na+m;   \n",
+      "md=M-M23Na;     #mass deficiency(u)\n",
+      "BE=md*E;    #binding energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"binding energy is\",round(BE,1),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "binding energy is 12.4 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 17.7, Page number 341"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "hbar=1.05*10**-34;   \n",
+      "c=3*10**8;   #speed of light(m/s)\n",
+      "mpi=140;    #mass of pi-meson(MeV/c**2)\n",
+      "e=1.6*10**-13;\n",
+      "\n",
+      "#Calculation\n",
+      "r=hbar*c/(mpi*e);    #range of nuclear force(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"range of nuclear force is\",round(r*10**15,1),\"fm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "range of nuclear force is 1.4 fm\n"
+       ]
+      }
+     ],
+     "prompt_number": 13
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter18.ipynb b/Modern_Physics_By_G.Aruldas/Chapter18.ipynb
new file mode 100755
index 00000000..b99ff137
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter18.ipynb
@@ -0,0 +1,366 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:0f6dea1f19194326599a9bca2989e912ed17e32f1ffb8d9305e16c13f8cacf2c"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "18: Radioactive decay"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.1, Page number 347"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "N0=1;   #assume\n",
+      "\n",
+      "#Calculation\n",
+      "f=(N0/2)/N0;   #fraction after t1/2\n",
+      "f1=(N0/4)/N0;   #fraction after 2 half lives\n",
+      "f2=(N0/(2**5))/N0;   #fraction after 5 half lives\n",
+      "f3=(N0/(2**10))/N0;   #fraction after 10 half lives\n",
+      "\n",
+      "#Result\n",
+      "print \"fraction after 2 half lives is\",f1\n",
+      "print \"fraction after 5 half lives is\",f2\n",
+      "print \"fraction after 10 half lives is\",f3"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "fraction after 2 half lives is 0.25\n",
+        "fraction after 5 half lives is 0.03125\n",
+        "fraction after 10 half lives is 0.0009765625\n"
+       ]
+      }
+     ],
+     "prompt_number": 1
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.2, Page number 348"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "thalf=2.7*24*60*60;   #half life(s)\n",
+      "m=1*10**-6;   #mass(gm)\n",
+      "Na=6.02*10**23;   #avagadro number(atoms/mol)\n",
+      "M=198;    #molar mass(g/mol)\n",
+      "t=8*24*60*60;\n",
+      "\n",
+      "#Calculation\n",
+      "lamda=0.693/thalf;    #decay constant(per sec)\n",
+      "N=m*Na/M;    #number of nuclei(atoms)\n",
+      "A0=lamda*N;    #activity(disintegrations per sec)\n",
+      "A=A0*math.exp(-lamda*t);    #activity for 8 days(decays per sec)\n",
+      "\n",
+      "#Result\n",
+      "print \"decay constant is\",round(lamda*10**6,2),\"*10**-6 per sec\"\n",
+      "print \"activity is\",round(A0/10**9,2),\"*10**9 disintegrations per sec\"\n",
+      "print \"activity for 8 days is\",round(A/10**9,2),\"*10**9 decays per sec\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "decay constant is 2.97 *10**-6 per sec\n",
+        "activity is 9.03 *10**9 disintegrations per sec\n",
+        "activity for 8 days is 1.16 *10**9 decays per sec\n"
+       ]
+      }
+     ],
+     "prompt_number": 10
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.3, Page number 348"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "thalf=5570*365*24*60*60;   #half life(s)\n",
+      "dNbydt=3.7*10**10*2*10**-3;   #number of decays per sec\n",
+      "m=14;\n",
+      "Na=6.02*10**23;   #avagadro number(atoms/mol)\n",
+      "\n",
+      "#Calculation\n",
+      "lamda=0.693/thalf;    #decay constant(per sec)\n",
+      "N=dNbydt/lamda;    #number of atoms\n",
+      "mN=m*N/Na;   #mass of 2mCi(g)\n",
+      "\n",
+      "#Result\n",
+      "print \"mass of 2mCi is\",round(mN*10**4,2),\"*10**-4 g\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "mass of 2mCi is 4.36 *10**-4 g\n"
+       ]
+      }
+     ],
+     "prompt_number": 23
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.5, Page number 353"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "thalf=1.25*10**9;   #half life(yr)\n",
+      "r=10.2;   #ratio of number of atoms\n",
+      "\n",
+      "#Calculation\n",
+      "a=1+r;\n",
+      "lamda=0.693/thalf;    #decay constant(per yr)\n",
+      "t=math.log(a)/lamda;   #time(yr)\n",
+      "\n",
+      "#Result\n",
+      "print \"the rock is\",round(t/10**9,2),\"*10**9 yrs old\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "the rock is 4.36 *10**9 yrs old\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.6, Page number 356"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mU=232.037131;    #atomic mass of U(u)\n",
+      "mHe=4.002603;   #atomic mass of He(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "KE=5.32;   #kinetic energy of alpha particle(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "mTh=mU-mHe-(KE/E);   #atomic mass of Th(u)\n",
+      "\n",
+      "#Result\n",
+      "print \"atomic mass of Th is\",round(mTh,5),\"u\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "atomic mass of Th is 228.02882 u\n"
+       ]
+      }
+     ],
+     "prompt_number": 14
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.7, Page number 359"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "E=931.5;    #energy(MeV)\n",
+      "mX=11.011433;   #mass of 11C(u)\n",
+      "mXdash=11.009305;  #mass of 11B(u)\n",
+      "me=0.511;\n",
+      "\n",
+      "#Calculation\n",
+      "Q=(E*(mX-mXdash))-(2*me);    #Q value for decay(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"maximum energy is\",round(Q,2),\"MeV.minimum energy is zero\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "maximum energy is 0.96 MeV.minimum energy is zero\n"
+       ]
+      }
+     ],
+     "prompt_number": 16
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.8, Page number 359"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mK=39.963999;    #mass of K(u)\n",
+      "mAr=39.962384;   #mass of Ar(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Q=(mK-mAr)*E;   #kinetic energy of neutrino(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"kinetic energy of neutrino is\",round(Q,3),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "kinetic energy of neutrino is 1.504 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 18
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.9, Page number 360"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mN=12.018613;    #mass of N(u)\n",
+      "mC=12;   #mass of C(u)\n",
+      "me=0.000549;   #mass of me(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "Egamma=4.43;   #energy of emitted gamma ray(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Q=(mN-mC-(2*me))*E;   #Q value(MeV)\n",
+      "Emax=Q-Egamma;   #maximum kinetic energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"maximum kinetic energy is\",round(Emax,2),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "maximum kinetic energy is 11.89 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 20
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter18_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter18_1.ipynb
new file mode 100755
index 00000000..b99ff137
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter18_1.ipynb
@@ -0,0 +1,366 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:0f6dea1f19194326599a9bca2989e912ed17e32f1ffb8d9305e16c13f8cacf2c"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "18: Radioactive decay"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.1, Page number 347"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "N0=1;   #assume\n",
+      "\n",
+      "#Calculation\n",
+      "f=(N0/2)/N0;   #fraction after t1/2\n",
+      "f1=(N0/4)/N0;   #fraction after 2 half lives\n",
+      "f2=(N0/(2**5))/N0;   #fraction after 5 half lives\n",
+      "f3=(N0/(2**10))/N0;   #fraction after 10 half lives\n",
+      "\n",
+      "#Result\n",
+      "print \"fraction after 2 half lives is\",f1\n",
+      "print \"fraction after 5 half lives is\",f2\n",
+      "print \"fraction after 10 half lives is\",f3"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "fraction after 2 half lives is 0.25\n",
+        "fraction after 5 half lives is 0.03125\n",
+        "fraction after 10 half lives is 0.0009765625\n"
+       ]
+      }
+     ],
+     "prompt_number": 1
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.2, Page number 348"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "thalf=2.7*24*60*60;   #half life(s)\n",
+      "m=1*10**-6;   #mass(gm)\n",
+      "Na=6.02*10**23;   #avagadro number(atoms/mol)\n",
+      "M=198;    #molar mass(g/mol)\n",
+      "t=8*24*60*60;\n",
+      "\n",
+      "#Calculation\n",
+      "lamda=0.693/thalf;    #decay constant(per sec)\n",
+      "N=m*Na/M;    #number of nuclei(atoms)\n",
+      "A0=lamda*N;    #activity(disintegrations per sec)\n",
+      "A=A0*math.exp(-lamda*t);    #activity for 8 days(decays per sec)\n",
+      "\n",
+      "#Result\n",
+      "print \"decay constant is\",round(lamda*10**6,2),\"*10**-6 per sec\"\n",
+      "print \"activity is\",round(A0/10**9,2),\"*10**9 disintegrations per sec\"\n",
+      "print \"activity for 8 days is\",round(A/10**9,2),\"*10**9 decays per sec\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "decay constant is 2.97 *10**-6 per sec\n",
+        "activity is 9.03 *10**9 disintegrations per sec\n",
+        "activity for 8 days is 1.16 *10**9 decays per sec\n"
+       ]
+      }
+     ],
+     "prompt_number": 10
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.3, Page number 348"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "thalf=5570*365*24*60*60;   #half life(s)\n",
+      "dNbydt=3.7*10**10*2*10**-3;   #number of decays per sec\n",
+      "m=14;\n",
+      "Na=6.02*10**23;   #avagadro number(atoms/mol)\n",
+      "\n",
+      "#Calculation\n",
+      "lamda=0.693/thalf;    #decay constant(per sec)\n",
+      "N=dNbydt/lamda;    #number of atoms\n",
+      "mN=m*N/Na;   #mass of 2mCi(g)\n",
+      "\n",
+      "#Result\n",
+      "print \"mass of 2mCi is\",round(mN*10**4,2),\"*10**-4 g\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "mass of 2mCi is 4.36 *10**-4 g\n"
+       ]
+      }
+     ],
+     "prompt_number": 23
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.5, Page number 353"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "thalf=1.25*10**9;   #half life(yr)\n",
+      "r=10.2;   #ratio of number of atoms\n",
+      "\n",
+      "#Calculation\n",
+      "a=1+r;\n",
+      "lamda=0.693/thalf;    #decay constant(per yr)\n",
+      "t=math.log(a)/lamda;   #time(yr)\n",
+      "\n",
+      "#Result\n",
+      "print \"the rock is\",round(t/10**9,2),\"*10**9 yrs old\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "the rock is 4.36 *10**9 yrs old\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.6, Page number 356"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mU=232.037131;    #atomic mass of U(u)\n",
+      "mHe=4.002603;   #atomic mass of He(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "KE=5.32;   #kinetic energy of alpha particle(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "mTh=mU-mHe-(KE/E);   #atomic mass of Th(u)\n",
+      "\n",
+      "#Result\n",
+      "print \"atomic mass of Th is\",round(mTh,5),\"u\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "atomic mass of Th is 228.02882 u\n"
+       ]
+      }
+     ],
+     "prompt_number": 14
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.7, Page number 359"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "E=931.5;    #energy(MeV)\n",
+      "mX=11.011433;   #mass of 11C(u)\n",
+      "mXdash=11.009305;  #mass of 11B(u)\n",
+      "me=0.511;\n",
+      "\n",
+      "#Calculation\n",
+      "Q=(E*(mX-mXdash))-(2*me);    #Q value for decay(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"maximum energy is\",round(Q,2),\"MeV.minimum energy is zero\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "maximum energy is 0.96 MeV.minimum energy is zero\n"
+       ]
+      }
+     ],
+     "prompt_number": 16
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.8, Page number 359"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mK=39.963999;    #mass of K(u)\n",
+      "mAr=39.962384;   #mass of Ar(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Q=(mK-mAr)*E;   #kinetic energy of neutrino(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"kinetic energy of neutrino is\",round(Q,3),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "kinetic energy of neutrino is 1.504 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 18
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.9, Page number 360"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mN=12.018613;    #mass of N(u)\n",
+      "mC=12;   #mass of C(u)\n",
+      "me=0.000549;   #mass of me(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "Egamma=4.43;   #energy of emitted gamma ray(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Q=(mN-mC-(2*me))*E;   #Q value(MeV)\n",
+      "Emax=Q-Egamma;   #maximum kinetic energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"maximum kinetic energy is\",round(Emax,2),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "maximum kinetic energy is 11.89 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 20
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter18_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter18_2.ipynb
new file mode 100755
index 00000000..b99ff137
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter18_2.ipynb
@@ -0,0 +1,366 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:0f6dea1f19194326599a9bca2989e912ed17e32f1ffb8d9305e16c13f8cacf2c"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "18: Radioactive decay"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.1, Page number 347"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "N0=1;   #assume\n",
+      "\n",
+      "#Calculation\n",
+      "f=(N0/2)/N0;   #fraction after t1/2\n",
+      "f1=(N0/4)/N0;   #fraction after 2 half lives\n",
+      "f2=(N0/(2**5))/N0;   #fraction after 5 half lives\n",
+      "f3=(N0/(2**10))/N0;   #fraction after 10 half lives\n",
+      "\n",
+      "#Result\n",
+      "print \"fraction after 2 half lives is\",f1\n",
+      "print \"fraction after 5 half lives is\",f2\n",
+      "print \"fraction after 10 half lives is\",f3"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "fraction after 2 half lives is 0.25\n",
+        "fraction after 5 half lives is 0.03125\n",
+        "fraction after 10 half lives is 0.0009765625\n"
+       ]
+      }
+     ],
+     "prompt_number": 1
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.2, Page number 348"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "thalf=2.7*24*60*60;   #half life(s)\n",
+      "m=1*10**-6;   #mass(gm)\n",
+      "Na=6.02*10**23;   #avagadro number(atoms/mol)\n",
+      "M=198;    #molar mass(g/mol)\n",
+      "t=8*24*60*60;\n",
+      "\n",
+      "#Calculation\n",
+      "lamda=0.693/thalf;    #decay constant(per sec)\n",
+      "N=m*Na/M;    #number of nuclei(atoms)\n",
+      "A0=lamda*N;    #activity(disintegrations per sec)\n",
+      "A=A0*math.exp(-lamda*t);    #activity for 8 days(decays per sec)\n",
+      "\n",
+      "#Result\n",
+      "print \"decay constant is\",round(lamda*10**6,2),\"*10**-6 per sec\"\n",
+      "print \"activity is\",round(A0/10**9,2),\"*10**9 disintegrations per sec\"\n",
+      "print \"activity for 8 days is\",round(A/10**9,2),\"*10**9 decays per sec\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "decay constant is 2.97 *10**-6 per sec\n",
+        "activity is 9.03 *10**9 disintegrations per sec\n",
+        "activity for 8 days is 1.16 *10**9 decays per sec\n"
+       ]
+      }
+     ],
+     "prompt_number": 10
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.3, Page number 348"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "thalf=5570*365*24*60*60;   #half life(s)\n",
+      "dNbydt=3.7*10**10*2*10**-3;   #number of decays per sec\n",
+      "m=14;\n",
+      "Na=6.02*10**23;   #avagadro number(atoms/mol)\n",
+      "\n",
+      "#Calculation\n",
+      "lamda=0.693/thalf;    #decay constant(per sec)\n",
+      "N=dNbydt/lamda;    #number of atoms\n",
+      "mN=m*N/Na;   #mass of 2mCi(g)\n",
+      "\n",
+      "#Result\n",
+      "print \"mass of 2mCi is\",round(mN*10**4,2),\"*10**-4 g\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "mass of 2mCi is 4.36 *10**-4 g\n"
+       ]
+      }
+     ],
+     "prompt_number": 23
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.5, Page number 353"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "thalf=1.25*10**9;   #half life(yr)\n",
+      "r=10.2;   #ratio of number of atoms\n",
+      "\n",
+      "#Calculation\n",
+      "a=1+r;\n",
+      "lamda=0.693/thalf;    #decay constant(per yr)\n",
+      "t=math.log(a)/lamda;   #time(yr)\n",
+      "\n",
+      "#Result\n",
+      "print \"the rock is\",round(t/10**9,2),\"*10**9 yrs old\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "the rock is 4.36 *10**9 yrs old\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.6, Page number 356"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mU=232.037131;    #atomic mass of U(u)\n",
+      "mHe=4.002603;   #atomic mass of He(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "KE=5.32;   #kinetic energy of alpha particle(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "mTh=mU-mHe-(KE/E);   #atomic mass of Th(u)\n",
+      "\n",
+      "#Result\n",
+      "print \"atomic mass of Th is\",round(mTh,5),\"u\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "atomic mass of Th is 228.02882 u\n"
+       ]
+      }
+     ],
+     "prompt_number": 14
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.7, Page number 359"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "E=931.5;    #energy(MeV)\n",
+      "mX=11.011433;   #mass of 11C(u)\n",
+      "mXdash=11.009305;  #mass of 11B(u)\n",
+      "me=0.511;\n",
+      "\n",
+      "#Calculation\n",
+      "Q=(E*(mX-mXdash))-(2*me);    #Q value for decay(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"maximum energy is\",round(Q,2),\"MeV.minimum energy is zero\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "maximum energy is 0.96 MeV.minimum energy is zero\n"
+       ]
+      }
+     ],
+     "prompt_number": 16
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.8, Page number 359"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mK=39.963999;    #mass of K(u)\n",
+      "mAr=39.962384;   #mass of Ar(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Q=(mK-mAr)*E;   #kinetic energy of neutrino(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"kinetic energy of neutrino is\",round(Q,3),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "kinetic energy of neutrino is 1.504 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 18
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.9, Page number 360"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mN=12.018613;    #mass of N(u)\n",
+      "mC=12;   #mass of C(u)\n",
+      "me=0.000549;   #mass of me(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "Egamma=4.43;   #energy of emitted gamma ray(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Q=(mN-mC-(2*me))*E;   #Q value(MeV)\n",
+      "Emax=Q-Egamma;   #maximum kinetic energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"maximum kinetic energy is\",round(Emax,2),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "maximum kinetic energy is 11.89 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 20
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter18_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter18_3.ipynb
new file mode 100755
index 00000000..b99ff137
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter18_3.ipynb
@@ -0,0 +1,366 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:0f6dea1f19194326599a9bca2989e912ed17e32f1ffb8d9305e16c13f8cacf2c"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "18: Radioactive decay"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.1, Page number 347"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "N0=1;   #assume\n",
+      "\n",
+      "#Calculation\n",
+      "f=(N0/2)/N0;   #fraction after t1/2\n",
+      "f1=(N0/4)/N0;   #fraction after 2 half lives\n",
+      "f2=(N0/(2**5))/N0;   #fraction after 5 half lives\n",
+      "f3=(N0/(2**10))/N0;   #fraction after 10 half lives\n",
+      "\n",
+      "#Result\n",
+      "print \"fraction after 2 half lives is\",f1\n",
+      "print \"fraction after 5 half lives is\",f2\n",
+      "print \"fraction after 10 half lives is\",f3"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "fraction after 2 half lives is 0.25\n",
+        "fraction after 5 half lives is 0.03125\n",
+        "fraction after 10 half lives is 0.0009765625\n"
+       ]
+      }
+     ],
+     "prompt_number": 1
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.2, Page number 348"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "thalf=2.7*24*60*60;   #half life(s)\n",
+      "m=1*10**-6;   #mass(gm)\n",
+      "Na=6.02*10**23;   #avagadro number(atoms/mol)\n",
+      "M=198;    #molar mass(g/mol)\n",
+      "t=8*24*60*60;\n",
+      "\n",
+      "#Calculation\n",
+      "lamda=0.693/thalf;    #decay constant(per sec)\n",
+      "N=m*Na/M;    #number of nuclei(atoms)\n",
+      "A0=lamda*N;    #activity(disintegrations per sec)\n",
+      "A=A0*math.exp(-lamda*t);    #activity for 8 days(decays per sec)\n",
+      "\n",
+      "#Result\n",
+      "print \"decay constant is\",round(lamda*10**6,2),\"*10**-6 per sec\"\n",
+      "print \"activity is\",round(A0/10**9,2),\"*10**9 disintegrations per sec\"\n",
+      "print \"activity for 8 days is\",round(A/10**9,2),\"*10**9 decays per sec\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "decay constant is 2.97 *10**-6 per sec\n",
+        "activity is 9.03 *10**9 disintegrations per sec\n",
+        "activity for 8 days is 1.16 *10**9 decays per sec\n"
+       ]
+      }
+     ],
+     "prompt_number": 10
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.3, Page number 348"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "thalf=5570*365*24*60*60;   #half life(s)\n",
+      "dNbydt=3.7*10**10*2*10**-3;   #number of decays per sec\n",
+      "m=14;\n",
+      "Na=6.02*10**23;   #avagadro number(atoms/mol)\n",
+      "\n",
+      "#Calculation\n",
+      "lamda=0.693/thalf;    #decay constant(per sec)\n",
+      "N=dNbydt/lamda;    #number of atoms\n",
+      "mN=m*N/Na;   #mass of 2mCi(g)\n",
+      "\n",
+      "#Result\n",
+      "print \"mass of 2mCi is\",round(mN*10**4,2),\"*10**-4 g\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "mass of 2mCi is 4.36 *10**-4 g\n"
+       ]
+      }
+     ],
+     "prompt_number": 23
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.5, Page number 353"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "thalf=1.25*10**9;   #half life(yr)\n",
+      "r=10.2;   #ratio of number of atoms\n",
+      "\n",
+      "#Calculation\n",
+      "a=1+r;\n",
+      "lamda=0.693/thalf;    #decay constant(per yr)\n",
+      "t=math.log(a)/lamda;   #time(yr)\n",
+      "\n",
+      "#Result\n",
+      "print \"the rock is\",round(t/10**9,2),\"*10**9 yrs old\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "the rock is 4.36 *10**9 yrs old\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.6, Page number 356"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mU=232.037131;    #atomic mass of U(u)\n",
+      "mHe=4.002603;   #atomic mass of He(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "KE=5.32;   #kinetic energy of alpha particle(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "mTh=mU-mHe-(KE/E);   #atomic mass of Th(u)\n",
+      "\n",
+      "#Result\n",
+      "print \"atomic mass of Th is\",round(mTh,5),\"u\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "atomic mass of Th is 228.02882 u\n"
+       ]
+      }
+     ],
+     "prompt_number": 14
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.7, Page number 359"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "E=931.5;    #energy(MeV)\n",
+      "mX=11.011433;   #mass of 11C(u)\n",
+      "mXdash=11.009305;  #mass of 11B(u)\n",
+      "me=0.511;\n",
+      "\n",
+      "#Calculation\n",
+      "Q=(E*(mX-mXdash))-(2*me);    #Q value for decay(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"maximum energy is\",round(Q,2),\"MeV.minimum energy is zero\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "maximum energy is 0.96 MeV.minimum energy is zero\n"
+       ]
+      }
+     ],
+     "prompt_number": 16
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.8, Page number 359"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mK=39.963999;    #mass of K(u)\n",
+      "mAr=39.962384;   #mass of Ar(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Q=(mK-mAr)*E;   #kinetic energy of neutrino(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"kinetic energy of neutrino is\",round(Q,3),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "kinetic energy of neutrino is 1.504 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 18
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 18.9, Page number 360"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mN=12.018613;    #mass of N(u)\n",
+      "mC=12;   #mass of C(u)\n",
+      "me=0.000549;   #mass of me(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "Egamma=4.43;   #energy of emitted gamma ray(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Q=(mN-mC-(2*me))*E;   #Q value(MeV)\n",
+      "Emax=Q-Egamma;   #maximum kinetic energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"maximum kinetic energy is\",round(Emax,2),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "maximum kinetic energy is 11.89 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 20
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter19.ipynb b/Modern_Physics_By_G.Aruldas/Chapter19.ipynb
new file mode 100755
index 00000000..c8745970
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter19.ipynb
@@ -0,0 +1,291 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:9326f276d5dc99ce97d41c9ca0d5924dbd68f522091536657f41d8cfe038dc31"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "19: Nuclear reactions"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.1, Page number 368"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m2H=2.014102;    #atomic mass of 2H(u)\n",
+      "mn=1.008665;    #mass of n(u)\n",
+      "m63Cu=62.929599;   #mass of 63Cu(u)\n",
+      "m64Zn=63.929144;   #mass of m64Zn(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "Kx=10;   #energy of deutron(MeV)\n",
+      "Ky=15;   #energy of neutron(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Q=E*(m2H+m63Cu-mn-m64Zn);    #Q-value(MeV)\n",
+      "KY=Q+Kx-Ky;    #kinetic energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"Q-value is\",round(Q,3),\"MeV\"\n",
+      "print \"kinetic energy is\",round(KY,3),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "Q-value is 5.488 MeV\n",
+        "kinetic energy is 0.488 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.2, Page number 368"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m19F=18.998404;    #atomic mass of 19F(u)\n",
+      "mH=1.007825;   #mass of H(u)\n",
+      "m19O=19.003577;   #mass of 19O(u)\n",
+      "mn=1.008665;   #mass of n(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Q=E*(m19F+mn-mH-m19O);    #Q-value(MeV)\n",
+      "Kxmin=-Q*(1+(mn/m19F));   #threshold energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"Q-value is\",round(Q,4),\"MeV\"\n",
+      "print \"threshold energy is\",round(Kxmin,2),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "Q-value is -4.0362 MeV\n",
+        "threshold energy is 4.25 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.3, Page number 373"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mn=1.008665;   #mass of n(u)\n",
+      "mu=235.043924;    #mass of 235U(u)\n",
+      "mBa=140.91440;    #mass of 141Ba(u)\n",
+      "mKr=91.92630;    #mass of Kr(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "mr=mn+mu;    #mass of reactants(u)\n",
+      "mp=mBa+mKr+(3*mn);   #mass of products(u)\n",
+      "md=mr-mp;   #mass difference(u)\n",
+      "E=md*E;    #energy released(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy released is\",round(E,1),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy released is 173.2 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 19
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.4, Page number 373"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "E=200*10**6;    #energy released(eV)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "P=300*10**6;   #power(W)\n",
+      "t=1;    #time(s)\n",
+      "\n",
+      "#Calculation\n",
+      "n=P*t/(E*e);    #number of fissions per second\n",
+      "\n",
+      "#Result\n",
+      "print \"number of fissions per second is\",n"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "number of fissions per second is 9.375e+18\n"
+       ]
+      }
+     ],
+     "prompt_number": 20
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.5, Page number 378"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m2H1=2*1.66*10**-27;    #mass of proton(kg)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "m1=2.014102;\n",
+      "m2=3.01609;\n",
+      "mH=1.007825;   #mass of H(u)\n",
+      "\n",
+      "#Calculation\n",
+      "E=E*((2*m1)-m2-mH);    #energy released(MeV)\n",
+      "n=0.001/m2H1;    #number of nuclei\n",
+      "Eg=n*E/2;   #energy released per gm(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy released per gm is\",round(Eg/10**23,2),\"*10**23 MeV\"\n",
+      "print \"answer given in the book is wrong\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy released per gm is 6.02 *10**23 MeV\n",
+        "answer given in the book is wrong\n"
+       ]
+      }
+     ],
+     "prompt_number": 31
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.6, Page number 379"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "k=8.99*10**9;   #value of k(Nm**2/C**2)\n",
+      "rd=1.5*10**-15;   #radius of deuterium nucleus(m)\n",
+      "rt=1.7*10**-15;   #radius of tritium nucleus(m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "KE=0.225;    #kinetic energy for 1 particle(MeV)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "\n",
+      "#Calculation\n",
+      "K_E=k*e**2/(e*(rd+rt));    #kinetic energy of 2 particles(MeV)\n",
+      "T=2*KE*e*10**6/(3*k);   #temperature(K)\n",
+      "\n",
+      "#Result\n",
+      "print \"temperature is\",round(T/10**9),\"*10**9 K\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "temperature is 2.0 *10**9 K\n"
+       ]
+      }
+     ],
+     "prompt_number": 35
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter19_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter19_1.ipynb
new file mode 100755
index 00000000..c8745970
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter19_1.ipynb
@@ -0,0 +1,291 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:9326f276d5dc99ce97d41c9ca0d5924dbd68f522091536657f41d8cfe038dc31"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "19: Nuclear reactions"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.1, Page number 368"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m2H=2.014102;    #atomic mass of 2H(u)\n",
+      "mn=1.008665;    #mass of n(u)\n",
+      "m63Cu=62.929599;   #mass of 63Cu(u)\n",
+      "m64Zn=63.929144;   #mass of m64Zn(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "Kx=10;   #energy of deutron(MeV)\n",
+      "Ky=15;   #energy of neutron(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Q=E*(m2H+m63Cu-mn-m64Zn);    #Q-value(MeV)\n",
+      "KY=Q+Kx-Ky;    #kinetic energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"Q-value is\",round(Q,3),\"MeV\"\n",
+      "print \"kinetic energy is\",round(KY,3),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "Q-value is 5.488 MeV\n",
+        "kinetic energy is 0.488 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.2, Page number 368"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m19F=18.998404;    #atomic mass of 19F(u)\n",
+      "mH=1.007825;   #mass of H(u)\n",
+      "m19O=19.003577;   #mass of 19O(u)\n",
+      "mn=1.008665;   #mass of n(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Q=E*(m19F+mn-mH-m19O);    #Q-value(MeV)\n",
+      "Kxmin=-Q*(1+(mn/m19F));   #threshold energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"Q-value is\",round(Q,4),\"MeV\"\n",
+      "print \"threshold energy is\",round(Kxmin,2),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "Q-value is -4.0362 MeV\n",
+        "threshold energy is 4.25 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.3, Page number 373"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mn=1.008665;   #mass of n(u)\n",
+      "mu=235.043924;    #mass of 235U(u)\n",
+      "mBa=140.91440;    #mass of 141Ba(u)\n",
+      "mKr=91.92630;    #mass of Kr(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "mr=mn+mu;    #mass of reactants(u)\n",
+      "mp=mBa+mKr+(3*mn);   #mass of products(u)\n",
+      "md=mr-mp;   #mass difference(u)\n",
+      "E=md*E;    #energy released(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy released is\",round(E,1),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy released is 173.2 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 19
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.4, Page number 373"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "E=200*10**6;    #energy released(eV)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "P=300*10**6;   #power(W)\n",
+      "t=1;    #time(s)\n",
+      "\n",
+      "#Calculation\n",
+      "n=P*t/(E*e);    #number of fissions per second\n",
+      "\n",
+      "#Result\n",
+      "print \"number of fissions per second is\",n"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "number of fissions per second is 9.375e+18\n"
+       ]
+      }
+     ],
+     "prompt_number": 20
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.5, Page number 378"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m2H1=2*1.66*10**-27;    #mass of proton(kg)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "m1=2.014102;\n",
+      "m2=3.01609;\n",
+      "mH=1.007825;   #mass of H(u)\n",
+      "\n",
+      "#Calculation\n",
+      "E=E*((2*m1)-m2-mH);    #energy released(MeV)\n",
+      "n=0.001/m2H1;    #number of nuclei\n",
+      "Eg=n*E/2;   #energy released per gm(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy released per gm is\",round(Eg/10**23,2),\"*10**23 MeV\"\n",
+      "print \"answer given in the book is wrong\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy released per gm is 6.02 *10**23 MeV\n",
+        "answer given in the book is wrong\n"
+       ]
+      }
+     ],
+     "prompt_number": 31
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.6, Page number 379"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "k=8.99*10**9;   #value of k(Nm**2/C**2)\n",
+      "rd=1.5*10**-15;   #radius of deuterium nucleus(m)\n",
+      "rt=1.7*10**-15;   #radius of tritium nucleus(m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "KE=0.225;    #kinetic energy for 1 particle(MeV)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "\n",
+      "#Calculation\n",
+      "K_E=k*e**2/(e*(rd+rt));    #kinetic energy of 2 particles(MeV)\n",
+      "T=2*KE*e*10**6/(3*k);   #temperature(K)\n",
+      "\n",
+      "#Result\n",
+      "print \"temperature is\",round(T/10**9),\"*10**9 K\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "temperature is 2.0 *10**9 K\n"
+       ]
+      }
+     ],
+     "prompt_number": 35
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter19_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter19_2.ipynb
new file mode 100755
index 00000000..c8745970
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter19_2.ipynb
@@ -0,0 +1,291 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:9326f276d5dc99ce97d41c9ca0d5924dbd68f522091536657f41d8cfe038dc31"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "19: Nuclear reactions"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.1, Page number 368"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m2H=2.014102;    #atomic mass of 2H(u)\n",
+      "mn=1.008665;    #mass of n(u)\n",
+      "m63Cu=62.929599;   #mass of 63Cu(u)\n",
+      "m64Zn=63.929144;   #mass of m64Zn(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "Kx=10;   #energy of deutron(MeV)\n",
+      "Ky=15;   #energy of neutron(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Q=E*(m2H+m63Cu-mn-m64Zn);    #Q-value(MeV)\n",
+      "KY=Q+Kx-Ky;    #kinetic energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"Q-value is\",round(Q,3),\"MeV\"\n",
+      "print \"kinetic energy is\",round(KY,3),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "Q-value is 5.488 MeV\n",
+        "kinetic energy is 0.488 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.2, Page number 368"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m19F=18.998404;    #atomic mass of 19F(u)\n",
+      "mH=1.007825;   #mass of H(u)\n",
+      "m19O=19.003577;   #mass of 19O(u)\n",
+      "mn=1.008665;   #mass of n(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Q=E*(m19F+mn-mH-m19O);    #Q-value(MeV)\n",
+      "Kxmin=-Q*(1+(mn/m19F));   #threshold energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"Q-value is\",round(Q,4),\"MeV\"\n",
+      "print \"threshold energy is\",round(Kxmin,2),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "Q-value is -4.0362 MeV\n",
+        "threshold energy is 4.25 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.3, Page number 373"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mn=1.008665;   #mass of n(u)\n",
+      "mu=235.043924;    #mass of 235U(u)\n",
+      "mBa=140.91440;    #mass of 141Ba(u)\n",
+      "mKr=91.92630;    #mass of Kr(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "mr=mn+mu;    #mass of reactants(u)\n",
+      "mp=mBa+mKr+(3*mn);   #mass of products(u)\n",
+      "md=mr-mp;   #mass difference(u)\n",
+      "E=md*E;    #energy released(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy released is\",round(E,1),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy released is 173.2 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 19
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.4, Page number 373"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "E=200*10**6;    #energy released(eV)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "P=300*10**6;   #power(W)\n",
+      "t=1;    #time(s)\n",
+      "\n",
+      "#Calculation\n",
+      "n=P*t/(E*e);    #number of fissions per second\n",
+      "\n",
+      "#Result\n",
+      "print \"number of fissions per second is\",n"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "number of fissions per second is 9.375e+18\n"
+       ]
+      }
+     ],
+     "prompt_number": 20
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.5, Page number 378"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m2H1=2*1.66*10**-27;    #mass of proton(kg)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "m1=2.014102;\n",
+      "m2=3.01609;\n",
+      "mH=1.007825;   #mass of H(u)\n",
+      "\n",
+      "#Calculation\n",
+      "E=E*((2*m1)-m2-mH);    #energy released(MeV)\n",
+      "n=0.001/m2H1;    #number of nuclei\n",
+      "Eg=n*E/2;   #energy released per gm(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy released per gm is\",round(Eg/10**23,2),\"*10**23 MeV\"\n",
+      "print \"answer given in the book is wrong\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy released per gm is 6.02 *10**23 MeV\n",
+        "answer given in the book is wrong\n"
+       ]
+      }
+     ],
+     "prompt_number": 31
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.6, Page number 379"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "k=8.99*10**9;   #value of k(Nm**2/C**2)\n",
+      "rd=1.5*10**-15;   #radius of deuterium nucleus(m)\n",
+      "rt=1.7*10**-15;   #radius of tritium nucleus(m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "KE=0.225;    #kinetic energy for 1 particle(MeV)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "\n",
+      "#Calculation\n",
+      "K_E=k*e**2/(e*(rd+rt));    #kinetic energy of 2 particles(MeV)\n",
+      "T=2*KE*e*10**6/(3*k);   #temperature(K)\n",
+      "\n",
+      "#Result\n",
+      "print \"temperature is\",round(T/10**9),\"*10**9 K\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "temperature is 2.0 *10**9 K\n"
+       ]
+      }
+     ],
+     "prompt_number": 35
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter19_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter19_3.ipynb
new file mode 100755
index 00000000..c8745970
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter19_3.ipynb
@@ -0,0 +1,291 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:9326f276d5dc99ce97d41c9ca0d5924dbd68f522091536657f41d8cfe038dc31"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "19: Nuclear reactions"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.1, Page number 368"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m2H=2.014102;    #atomic mass of 2H(u)\n",
+      "mn=1.008665;    #mass of n(u)\n",
+      "m63Cu=62.929599;   #mass of 63Cu(u)\n",
+      "m64Zn=63.929144;   #mass of m64Zn(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "Kx=10;   #energy of deutron(MeV)\n",
+      "Ky=15;   #energy of neutron(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Q=E*(m2H+m63Cu-mn-m64Zn);    #Q-value(MeV)\n",
+      "KY=Q+Kx-Ky;    #kinetic energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"Q-value is\",round(Q,3),\"MeV\"\n",
+      "print \"kinetic energy is\",round(KY,3),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "Q-value is 5.488 MeV\n",
+        "kinetic energy is 0.488 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.2, Page number 368"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m19F=18.998404;    #atomic mass of 19F(u)\n",
+      "mH=1.007825;   #mass of H(u)\n",
+      "m19O=19.003577;   #mass of 19O(u)\n",
+      "mn=1.008665;   #mass of n(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Q=E*(m19F+mn-mH-m19O);    #Q-value(MeV)\n",
+      "Kxmin=-Q*(1+(mn/m19F));   #threshold energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"Q-value is\",round(Q,4),\"MeV\"\n",
+      "print \"threshold energy is\",round(Kxmin,2),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "Q-value is -4.0362 MeV\n",
+        "threshold energy is 4.25 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.3, Page number 373"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mn=1.008665;   #mass of n(u)\n",
+      "mu=235.043924;    #mass of 235U(u)\n",
+      "mBa=140.91440;    #mass of 141Ba(u)\n",
+      "mKr=91.92630;    #mass of Kr(u)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "mr=mn+mu;    #mass of reactants(u)\n",
+      "mp=mBa+mKr+(3*mn);   #mass of products(u)\n",
+      "md=mr-mp;   #mass difference(u)\n",
+      "E=md*E;    #energy released(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy released is\",round(E,1),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy released is 173.2 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 19
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.4, Page number 373"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "E=200*10**6;    #energy released(eV)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "P=300*10**6;   #power(W)\n",
+      "t=1;    #time(s)\n",
+      "\n",
+      "#Calculation\n",
+      "n=P*t/(E*e);    #number of fissions per second\n",
+      "\n",
+      "#Result\n",
+      "print \"number of fissions per second is\",n"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "number of fissions per second is 9.375e+18\n"
+       ]
+      }
+     ],
+     "prompt_number": 20
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.5, Page number 378"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m2H1=2*1.66*10**-27;    #mass of proton(kg)\n",
+      "E=931.5;    #energy(MeV)\n",
+      "m1=2.014102;\n",
+      "m2=3.01609;\n",
+      "mH=1.007825;   #mass of H(u)\n",
+      "\n",
+      "#Calculation\n",
+      "E=E*((2*m1)-m2-mH);    #energy released(MeV)\n",
+      "n=0.001/m2H1;    #number of nuclei\n",
+      "Eg=n*E/2;   #energy released per gm(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy released per gm is\",round(Eg/10**23,2),\"*10**23 MeV\"\n",
+      "print \"answer given in the book is wrong\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy released per gm is 6.02 *10**23 MeV\n",
+        "answer given in the book is wrong\n"
+       ]
+      }
+     ],
+     "prompt_number": 31
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 19.6, Page number 379"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "k=8.99*10**9;   #value of k(Nm**2/C**2)\n",
+      "rd=1.5*10**-15;   #radius of deuterium nucleus(m)\n",
+      "rt=1.7*10**-15;   #radius of tritium nucleus(m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "KE=0.225;    #kinetic energy for 1 particle(MeV)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "\n",
+      "#Calculation\n",
+      "K_E=k*e**2/(e*(rd+rt));    #kinetic energy of 2 particles(MeV)\n",
+      "T=2*KE*e*10**6/(3*k);   #temperature(K)\n",
+      "\n",
+      "#Result\n",
+      "print \"temperature is\",round(T/10**9),\"*10**9 K\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "temperature is 2.0 *10**9 K\n"
+       ]
+      }
+     ],
+     "prompt_number": 35
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter1_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter1_1.ipynb
new file mode 100755
index 00000000..483d55f3
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter1_1.ipynb
@@ -0,0 +1,311 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:467ef5c6562d2c93b60e422b9b9a8c5a34323da84f6c33e87f513c3c578db36d"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "1: The special theory of relativity"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.2, Page number 10"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=1;   #assume\n",
+      "udash=0.9*c;   #speed of 2nd rocket\n",
+      "v=0.6*c;   #speed of 1st rocket\n",
+      "\n",
+      "#Calculation\n",
+      "u1=(udash+v)/(1+(udash*v/(c**2)));   #speed of 2nd rocket in same direction\n",
+      "u2=(-udash+v)/(1-(udash*v/(c**2)));   #speed of 2nd rocket in opposite direction\n",
+      "\n",
+      "#Result\n",
+      "print \"speed of 2nd rocket in same direction is\",round(u1,3),\"*c\"\n",
+      "print \"speed of 2nd rocket in opposite direction is\",round(u2,3),\"*c\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed of 2nd rocket in same direction is 0.974 *c\n",
+        "speed of 2nd rocket in opposite direction is -0.652 *c\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.3, Page number 12"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "#given L0-L/L0=0.01.so L=0.99*L0\n",
+      "LbyL0=0.99;\n",
+      "c=1;   #assume\n",
+      "\n",
+      "#Calculation\n",
+      "v2=(c**2)*(1-(LbyL0)**2);\n",
+      "v=math.sqrt(v2);    #speed\n",
+      "\n",
+      "#Result\n",
+      "print \"speed is\",round(v,3),\"*c\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed is 0.141 *c\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.4, Page number 12"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "delta_tow=2.6*10**-8;   #mean lifetime at rest(s)\n",
+      "d=20;   #distance(m)\n",
+      "c=3*10**8;   #speed of light(m/s)\n",
+      "\n",
+      "#Calculation\n",
+      "#delta_t=d/v\n",
+      "v2=(c**2)/(1+(delta_tow*c/d)**2);\n",
+      "v=math.sqrt(v2);   #speed of unstable particle(m/s)\n",
+      "\n",
+      "#Result\n",
+      "print \"speed of unstable particle is\",round(v/10**8,1),\"*10**8 m/s\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed of unstable particle is 2.8 *10**8 m/s\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.5, Page number 13"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "delta_t=5*10**-6;   #mean lifetime(s)\n",
+      "c=1;   #assume\n",
+      "v=0.9*c;   #speed of beam\n",
+      "\n",
+      "#Calculation\n",
+      "delta_tow=delta_t*math.sqrt(1-(v/c)**2);   #proper lifetime of particles(s)\n",
+      "\n",
+      "#Result\n",
+      "print \"proper lifetime of particles is\",round(delta_tow*10**6,2),\"*10**-6 s\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "proper lifetime of particles is 2.18 *10**-6 s\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.6, Page number 15"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=1;   #assume\n",
+      "m0bym=100/120;    #ratio of masses\n",
+      "\n",
+      "#Calculation\n",
+      "v=c*math.sqrt(1-(m0bym**2));     #speed of body\n",
+      "\n",
+      "#Result\n",
+      "print \"speed of body is\",round(v,3),\"*c\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed of body is 0.553 *c\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.7, Page number 17"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=3*10**8;   #speed of light(m/s)\n",
+      "deltaE=4*10**26;   #energy of sun(J/s)\n",
+      "\n",
+      "#Calculation\n",
+      "deltam=deltaE/c**2;   #change in mass(kg)\n",
+      "\n",
+      "#Result\n",
+      "print \"change in mass is\",round(deltam/10**9,2),\"*10**9 kg\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "change in mass is 4.44 *10**9 kg\n"
+       ]
+      }
+     ],
+     "prompt_number": 13
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.8, Page number 17"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=1;   #assume\n",
+      "T=10;   #kinetic energy(MeV)\n",
+      "m0c2=0.512;   #rest energy of electron(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "E=T+m0c2;   #total energy(MeV)\n",
+      "p=math.sqrt((E**2)-(m0c2**2))/c;    #momentum of electron(MeV/c)\n",
+      "v=c*math.sqrt(1-(m0c2/E)**2);    #velocity of electron(c)\n",
+      "\n",
+      "#Result\n",
+      "print \"momentum of electron is\",round(p,1),\"MeV/c\"\n",
+      "print \"velocity of electron is\",round(v,4),\"*c\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "momentum of electron is 10.5 MeV/c\n",
+        "velocity of electron is 0.9988 *c\n"
+       ]
+      }
+     ],
+     "prompt_number": 16
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter1_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter1_2.ipynb
new file mode 100755
index 00000000..483d55f3
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter1_2.ipynb
@@ -0,0 +1,311 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:467ef5c6562d2c93b60e422b9b9a8c5a34323da84f6c33e87f513c3c578db36d"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "1: The special theory of relativity"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.2, Page number 10"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=1;   #assume\n",
+      "udash=0.9*c;   #speed of 2nd rocket\n",
+      "v=0.6*c;   #speed of 1st rocket\n",
+      "\n",
+      "#Calculation\n",
+      "u1=(udash+v)/(1+(udash*v/(c**2)));   #speed of 2nd rocket in same direction\n",
+      "u2=(-udash+v)/(1-(udash*v/(c**2)));   #speed of 2nd rocket in opposite direction\n",
+      "\n",
+      "#Result\n",
+      "print \"speed of 2nd rocket in same direction is\",round(u1,3),\"*c\"\n",
+      "print \"speed of 2nd rocket in opposite direction is\",round(u2,3),\"*c\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed of 2nd rocket in same direction is 0.974 *c\n",
+        "speed of 2nd rocket in opposite direction is -0.652 *c\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.3, Page number 12"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "#given L0-L/L0=0.01.so L=0.99*L0\n",
+      "LbyL0=0.99;\n",
+      "c=1;   #assume\n",
+      "\n",
+      "#Calculation\n",
+      "v2=(c**2)*(1-(LbyL0)**2);\n",
+      "v=math.sqrt(v2);    #speed\n",
+      "\n",
+      "#Result\n",
+      "print \"speed is\",round(v,3),\"*c\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed is 0.141 *c\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.4, Page number 12"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "delta_tow=2.6*10**-8;   #mean lifetime at rest(s)\n",
+      "d=20;   #distance(m)\n",
+      "c=3*10**8;   #speed of light(m/s)\n",
+      "\n",
+      "#Calculation\n",
+      "#delta_t=d/v\n",
+      "v2=(c**2)/(1+(delta_tow*c/d)**2);\n",
+      "v=math.sqrt(v2);   #speed of unstable particle(m/s)\n",
+      "\n",
+      "#Result\n",
+      "print \"speed of unstable particle is\",round(v/10**8,1),\"*10**8 m/s\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed of unstable particle is 2.8 *10**8 m/s\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.5, Page number 13"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "delta_t=5*10**-6;   #mean lifetime(s)\n",
+      "c=1;   #assume\n",
+      "v=0.9*c;   #speed of beam\n",
+      "\n",
+      "#Calculation\n",
+      "delta_tow=delta_t*math.sqrt(1-(v/c)**2);   #proper lifetime of particles(s)\n",
+      "\n",
+      "#Result\n",
+      "print \"proper lifetime of particles is\",round(delta_tow*10**6,2),\"*10**-6 s\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "proper lifetime of particles is 2.18 *10**-6 s\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.6, Page number 15"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=1;   #assume\n",
+      "m0bym=100/120;    #ratio of masses\n",
+      "\n",
+      "#Calculation\n",
+      "v=c*math.sqrt(1-(m0bym**2));     #speed of body\n",
+      "\n",
+      "#Result\n",
+      "print \"speed of body is\",round(v,3),\"*c\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed of body is 0.553 *c\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.7, Page number 17"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=3*10**8;   #speed of light(m/s)\n",
+      "deltaE=4*10**26;   #energy of sun(J/s)\n",
+      "\n",
+      "#Calculation\n",
+      "deltam=deltaE/c**2;   #change in mass(kg)\n",
+      "\n",
+      "#Result\n",
+      "print \"change in mass is\",round(deltam/10**9,2),\"*10**9 kg\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "change in mass is 4.44 *10**9 kg\n"
+       ]
+      }
+     ],
+     "prompt_number": 13
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.8, Page number 17"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=1;   #assume\n",
+      "T=10;   #kinetic energy(MeV)\n",
+      "m0c2=0.512;   #rest energy of electron(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "E=T+m0c2;   #total energy(MeV)\n",
+      "p=math.sqrt((E**2)-(m0c2**2))/c;    #momentum of electron(MeV/c)\n",
+      "v=c*math.sqrt(1-(m0c2/E)**2);    #velocity of electron(c)\n",
+      "\n",
+      "#Result\n",
+      "print \"momentum of electron is\",round(p,1),\"MeV/c\"\n",
+      "print \"velocity of electron is\",round(v,4),\"*c\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "momentum of electron is 10.5 MeV/c\n",
+        "velocity of electron is 0.9988 *c\n"
+       ]
+      }
+     ],
+     "prompt_number": 16
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter1_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter1_3.ipynb
new file mode 100755
index 00000000..483d55f3
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter1_3.ipynb
@@ -0,0 +1,311 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:467ef5c6562d2c93b60e422b9b9a8c5a34323da84f6c33e87f513c3c578db36d"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "1: The special theory of relativity"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.2, Page number 10"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=1;   #assume\n",
+      "udash=0.9*c;   #speed of 2nd rocket\n",
+      "v=0.6*c;   #speed of 1st rocket\n",
+      "\n",
+      "#Calculation\n",
+      "u1=(udash+v)/(1+(udash*v/(c**2)));   #speed of 2nd rocket in same direction\n",
+      "u2=(-udash+v)/(1-(udash*v/(c**2)));   #speed of 2nd rocket in opposite direction\n",
+      "\n",
+      "#Result\n",
+      "print \"speed of 2nd rocket in same direction is\",round(u1,3),\"*c\"\n",
+      "print \"speed of 2nd rocket in opposite direction is\",round(u2,3),\"*c\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed of 2nd rocket in same direction is 0.974 *c\n",
+        "speed of 2nd rocket in opposite direction is -0.652 *c\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.3, Page number 12"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "#given L0-L/L0=0.01.so L=0.99*L0\n",
+      "LbyL0=0.99;\n",
+      "c=1;   #assume\n",
+      "\n",
+      "#Calculation\n",
+      "v2=(c**2)*(1-(LbyL0)**2);\n",
+      "v=math.sqrt(v2);    #speed\n",
+      "\n",
+      "#Result\n",
+      "print \"speed is\",round(v,3),\"*c\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed is 0.141 *c\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.4, Page number 12"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "delta_tow=2.6*10**-8;   #mean lifetime at rest(s)\n",
+      "d=20;   #distance(m)\n",
+      "c=3*10**8;   #speed of light(m/s)\n",
+      "\n",
+      "#Calculation\n",
+      "#delta_t=d/v\n",
+      "v2=(c**2)/(1+(delta_tow*c/d)**2);\n",
+      "v=math.sqrt(v2);   #speed of unstable particle(m/s)\n",
+      "\n",
+      "#Result\n",
+      "print \"speed of unstable particle is\",round(v/10**8,1),\"*10**8 m/s\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed of unstable particle is 2.8 *10**8 m/s\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.5, Page number 13"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "delta_t=5*10**-6;   #mean lifetime(s)\n",
+      "c=1;   #assume\n",
+      "v=0.9*c;   #speed of beam\n",
+      "\n",
+      "#Calculation\n",
+      "delta_tow=delta_t*math.sqrt(1-(v/c)**2);   #proper lifetime of particles(s)\n",
+      "\n",
+      "#Result\n",
+      "print \"proper lifetime of particles is\",round(delta_tow*10**6,2),\"*10**-6 s\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "proper lifetime of particles is 2.18 *10**-6 s\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.6, Page number 15"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=1;   #assume\n",
+      "m0bym=100/120;    #ratio of masses\n",
+      "\n",
+      "#Calculation\n",
+      "v=c*math.sqrt(1-(m0bym**2));     #speed of body\n",
+      "\n",
+      "#Result\n",
+      "print \"speed of body is\",round(v,3),\"*c\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "speed of body is 0.553 *c\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.7, Page number 17"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=3*10**8;   #speed of light(m/s)\n",
+      "deltaE=4*10**26;   #energy of sun(J/s)\n",
+      "\n",
+      "#Calculation\n",
+      "deltam=deltaE/c**2;   #change in mass(kg)\n",
+      "\n",
+      "#Result\n",
+      "print \"change in mass is\",round(deltam/10**9,2),\"*10**9 kg\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "change in mass is 4.44 *10**9 kg\n"
+       ]
+      }
+     ],
+     "prompt_number": 13
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 1.8, Page number 17"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=1;   #assume\n",
+      "T=10;   #kinetic energy(MeV)\n",
+      "m0c2=0.512;   #rest energy of electron(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "E=T+m0c2;   #total energy(MeV)\n",
+      "p=math.sqrt((E**2)-(m0c2**2))/c;    #momentum of electron(MeV/c)\n",
+      "v=c*math.sqrt(1-(m0c2/E)**2);    #velocity of electron(c)\n",
+      "\n",
+      "#Result\n",
+      "print \"momentum of electron is\",round(p,1),\"MeV/c\"\n",
+      "print \"velocity of electron is\",round(v,4),\"*c\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "momentum of electron is 10.5 MeV/c\n",
+        "velocity of electron is 0.9988 *c\n"
+       ]
+      }
+     ],
+     "prompt_number": 16
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter2.ipynb
new file mode 100755
index 00000000..59d9ea57
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter2.ipynb
@@ -0,0 +1,295 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:f048d58df41f2578c151ef59f03652004b6758b9e666d170255be2c66115bfe2"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "2: Particle nature of radiation"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.1, Page number 28"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "new=100*10**6;    #frequency(Hz)\n",
+      "P=100*10**3;    #power(watt)\n",
+      "\n",
+      "#Calculation\n",
+      "E=h*new;    #quantum of energy(J)\n",
+      "n=P/E;    #number of quanta emitted(per sec)\n",
+      "\n",
+      "#Result\n",
+      "print \"number of quanta emitted is\",round(n/10**29,2),\"*10**29 per sec\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "number of quanta emitted is 15.09 *10**29 per sec\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.2, Page number 31"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=400*10**-9;    #wavelength(m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "w0=2.28;    #work function(eV)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "E=h*c/(lamda*e);    #energy(eV)\n",
+      "KEmax=E-w0;    #maximum kinetic energy(eV)\n",
+      "v2=2*KEmax*e/m;  \n",
+      "v=math.sqrt(v2);   #velocity(m/s)\n",
+      "\n",
+      "#Result\n",
+      "print \"maximum kinetic energy is\",round(KEmax,3),\"eV\"\n",
+      "print \"velocity of photoelectrons is\",round(v/10**5,2),\"*10**5 m/s\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "maximum kinetic energy is 0.826 eV\n",
+        "velocity of photoelectrons is 5.39 *10**5 m/s\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.3, Page number 31"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=2000*10**-10;    #wavelength(m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "w0=4.2;    #work function(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "lamda0=h*c/(w0*e);   #cut off wavelength(m)\n",
+      "E=h*c/(lamda*e);    #energy(eV)\n",
+      "sp=E-w0;    #stopping potential(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"cut off wavelength is\",int(lamda0*10**10),\"angstrom\"\n",
+      "print \"stopping potential is\",round(sp,2),\"V\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "cut off wavelength is 2958 angstrom\n",
+        "stopping potential is 2.01 V\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.4, Page number 33"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=0.2*10**-9;    #wavelength(m)\n",
+      "\n",
+      "#Calculation\n",
+      "p=h/lamda;    #momentum(kg m/s)\n",
+      "m=p/c;   #effective mass(kg)\n",
+      "\n",
+      "#Result\n",
+      "print \"momentum is\",round(p*10**24,1),\"*10**-24 kg m/s\"\n",
+      "print \"effective mass is\",round(m*10**32,1),\"*10**-32 kg\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "momentum is 3.3 *10**-24 kg m/s\n",
+        "effective mass is 1.1 *10**-32 kg\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.5, Page number 35"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=0.15;    #wavelength(nm)\n",
+      "m0=9.1*10**-31;    #mass of electron(kg)\n",
+      "theta1=0;   #scattering angle1(degrees)\n",
+      "theta2=90;   #scattering angle2(degrees)\n",
+      "theta3=180;   #scattering angle3(degrees)\n",
+      "\n",
+      "#Calculation\n",
+      "theta1=theta1*math.pi/180;   #scattering angle1(radian)\n",
+      "theta2=theta2*math.pi/180;   #scattering angle2(radian)\n",
+      "theta3=theta3*math.pi/180;   #scattering angle3(radian)\n",
+      "lamda_dash1=lamda+(h*(1-math.cos(theta1))/(m0*c));   #wavelength at 0(nm)\n",
+      "lamda_dash2=lamda+(10**9*h*(1-math.cos(theta2))/(m0*c));   #wavelength at 90(nm)\n",
+      "lamda_dash3=lamda+(10**9*h*(1-math.cos(theta3))/(m0*c));   #wavelength at 180(nm)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength at 0 degrees is\",lamda_dash1,\"nm\"\n",
+      "print \"wavelength at 90 degrees is\",round(lamda_dash2,3),\"nm\"\n",
+      "print \"wavelength at 180 degrees is\",round(lamda_dash3,3),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength at 0 degrees is 0.15 nm\n",
+        "wavelength at 90 degrees is 0.152 nm\n",
+        "wavelength at 180 degrees is 0.155 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 18
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.6, Page number 36"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "E=2*0.511*10**6;   #rest energy(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "lamda=h*c/(E*e);    #wavelength of photon(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength of photon is\",round(lamda*10**12,2),\"*10**-12 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength of photon is 1.22 *10**-12 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 21
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter20.ipynb b/Modern_Physics_By_G.Aruldas/Chapter20.ipynb
new file mode 100755
index 00000000..6f977e4e
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter20.ipynb
@@ -0,0 +1,119 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:eeb9c551735bd0ab45890fc906baf874437271bf852063fccc60d822b2aaeaef"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "20: Nuclear radiation detectors and particle accelerators"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 20.1, Page number 390"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=1.67*10**-27;    #mass of proton(kg)\n",
+      "E=30*10**6;   #energy(eV)\n",
+      "r=1.2*10**-15;   #radius of nucleon(m)\n",
+      "\n",
+      "#Calculation\n",
+      "lamdaP=h/math.sqrt(2*m*E*e);   #wavelength of proton(m)\n",
+      "lamdaAlpha=h/math.sqrt(2*4*m*E*e);   #wavelength of alpha particle(m)\n",
+      "a=2*r;    #size of nucleon(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength of proton is\",round(lamdaP*10**15,1),\"*10**-15 m\"\n",
+      "print \"wavelength of alpha particle is\",round(lamdaAlpha*10**15,1),\"*10**-15 m\"\n",
+      "print \"size of nucleon is\",a,\"m\"\n",
+      "print \"alpha particle is better\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength of proton is 5.2 *10**-15 m\n",
+        "wavelength of alpha particle is 2.6 *10**-15 m\n",
+        "size of nucleon is 2.4e-15 m\n",
+        "alpha particle is better\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 20.2, Page number 391"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "q=1.6*10**-19;   #conversion factor from J to eV\n",
+      "B=2;   #magnetic field(T)\n",
+      "m=1.67*10**-27;    #mass of proton(kg)\n",
+      "R=0.25;   #radius(m)\n",
+      "a=6.24*10**12;   #conversion factor from J to MeV\n",
+      "\n",
+      "#Calculation\n",
+      "f=q*B/(2*math.pi*m);    #frequency needed(MHz)\n",
+      "KE=q**2*B**2*R**2/(2*m);   #kinetic energy(J)\n",
+      "KE=KE*a;     #kinetic energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"frequency needed is\",round(f*10**-6,1),\"MHz\"\n",
+      "print \"kinetic energy is\",round(KE),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "frequency needed is 30.5 MHz\n",
+        "kinetic energy is 12.0 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter20_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter20_1.ipynb
new file mode 100755
index 00000000..6f977e4e
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter20_1.ipynb
@@ -0,0 +1,119 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:eeb9c551735bd0ab45890fc906baf874437271bf852063fccc60d822b2aaeaef"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "20: Nuclear radiation detectors and particle accelerators"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 20.1, Page number 390"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=1.67*10**-27;    #mass of proton(kg)\n",
+      "E=30*10**6;   #energy(eV)\n",
+      "r=1.2*10**-15;   #radius of nucleon(m)\n",
+      "\n",
+      "#Calculation\n",
+      "lamdaP=h/math.sqrt(2*m*E*e);   #wavelength of proton(m)\n",
+      "lamdaAlpha=h/math.sqrt(2*4*m*E*e);   #wavelength of alpha particle(m)\n",
+      "a=2*r;    #size of nucleon(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength of proton is\",round(lamdaP*10**15,1),\"*10**-15 m\"\n",
+      "print \"wavelength of alpha particle is\",round(lamdaAlpha*10**15,1),\"*10**-15 m\"\n",
+      "print \"size of nucleon is\",a,\"m\"\n",
+      "print \"alpha particle is better\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength of proton is 5.2 *10**-15 m\n",
+        "wavelength of alpha particle is 2.6 *10**-15 m\n",
+        "size of nucleon is 2.4e-15 m\n",
+        "alpha particle is better\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 20.2, Page number 391"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "q=1.6*10**-19;   #conversion factor from J to eV\n",
+      "B=2;   #magnetic field(T)\n",
+      "m=1.67*10**-27;    #mass of proton(kg)\n",
+      "R=0.25;   #radius(m)\n",
+      "a=6.24*10**12;   #conversion factor from J to MeV\n",
+      "\n",
+      "#Calculation\n",
+      "f=q*B/(2*math.pi*m);    #frequency needed(MHz)\n",
+      "KE=q**2*B**2*R**2/(2*m);   #kinetic energy(J)\n",
+      "KE=KE*a;     #kinetic energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"frequency needed is\",round(f*10**-6,1),\"MHz\"\n",
+      "print \"kinetic energy is\",round(KE),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "frequency needed is 30.5 MHz\n",
+        "kinetic energy is 12.0 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter20_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter20_2.ipynb
new file mode 100755
index 00000000..6f977e4e
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter20_2.ipynb
@@ -0,0 +1,119 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:eeb9c551735bd0ab45890fc906baf874437271bf852063fccc60d822b2aaeaef"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "20: Nuclear radiation detectors and particle accelerators"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 20.1, Page number 390"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=1.67*10**-27;    #mass of proton(kg)\n",
+      "E=30*10**6;   #energy(eV)\n",
+      "r=1.2*10**-15;   #radius of nucleon(m)\n",
+      "\n",
+      "#Calculation\n",
+      "lamdaP=h/math.sqrt(2*m*E*e);   #wavelength of proton(m)\n",
+      "lamdaAlpha=h/math.sqrt(2*4*m*E*e);   #wavelength of alpha particle(m)\n",
+      "a=2*r;    #size of nucleon(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength of proton is\",round(lamdaP*10**15,1),\"*10**-15 m\"\n",
+      "print \"wavelength of alpha particle is\",round(lamdaAlpha*10**15,1),\"*10**-15 m\"\n",
+      "print \"size of nucleon is\",a,\"m\"\n",
+      "print \"alpha particle is better\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength of proton is 5.2 *10**-15 m\n",
+        "wavelength of alpha particle is 2.6 *10**-15 m\n",
+        "size of nucleon is 2.4e-15 m\n",
+        "alpha particle is better\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 20.2, Page number 391"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "q=1.6*10**-19;   #conversion factor from J to eV\n",
+      "B=2;   #magnetic field(T)\n",
+      "m=1.67*10**-27;    #mass of proton(kg)\n",
+      "R=0.25;   #radius(m)\n",
+      "a=6.24*10**12;   #conversion factor from J to MeV\n",
+      "\n",
+      "#Calculation\n",
+      "f=q*B/(2*math.pi*m);    #frequency needed(MHz)\n",
+      "KE=q**2*B**2*R**2/(2*m);   #kinetic energy(J)\n",
+      "KE=KE*a;     #kinetic energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"frequency needed is\",round(f*10**-6,1),\"MHz\"\n",
+      "print \"kinetic energy is\",round(KE),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "frequency needed is 30.5 MHz\n",
+        "kinetic energy is 12.0 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter20_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter20_3.ipynb
new file mode 100755
index 00000000..6f977e4e
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter20_3.ipynb
@@ -0,0 +1,119 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:eeb9c551735bd0ab45890fc906baf874437271bf852063fccc60d822b2aaeaef"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "20: Nuclear radiation detectors and particle accelerators"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 20.1, Page number 390"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=1.67*10**-27;    #mass of proton(kg)\n",
+      "E=30*10**6;   #energy(eV)\n",
+      "r=1.2*10**-15;   #radius of nucleon(m)\n",
+      "\n",
+      "#Calculation\n",
+      "lamdaP=h/math.sqrt(2*m*E*e);   #wavelength of proton(m)\n",
+      "lamdaAlpha=h/math.sqrt(2*4*m*E*e);   #wavelength of alpha particle(m)\n",
+      "a=2*r;    #size of nucleon(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength of proton is\",round(lamdaP*10**15,1),\"*10**-15 m\"\n",
+      "print \"wavelength of alpha particle is\",round(lamdaAlpha*10**15,1),\"*10**-15 m\"\n",
+      "print \"size of nucleon is\",a,\"m\"\n",
+      "print \"alpha particle is better\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength of proton is 5.2 *10**-15 m\n",
+        "wavelength of alpha particle is 2.6 *10**-15 m\n",
+        "size of nucleon is 2.4e-15 m\n",
+        "alpha particle is better\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 20.2, Page number 391"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "q=1.6*10**-19;   #conversion factor from J to eV\n",
+      "B=2;   #magnetic field(T)\n",
+      "m=1.67*10**-27;    #mass of proton(kg)\n",
+      "R=0.25;   #radius(m)\n",
+      "a=6.24*10**12;   #conversion factor from J to MeV\n",
+      "\n",
+      "#Calculation\n",
+      "f=q*B/(2*math.pi*m);    #frequency needed(MHz)\n",
+      "KE=q**2*B**2*R**2/(2*m);   #kinetic energy(J)\n",
+      "KE=KE*a;     #kinetic energy(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"frequency needed is\",round(f*10**-6,1),\"MHz\"\n",
+      "print \"kinetic energy is\",round(KE),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "frequency needed is 30.5 MHz\n",
+        "kinetic energy is 12.0 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter21.ipynb b/Modern_Physics_By_G.Aruldas/Chapter21.ipynb
new file mode 100755
index 00000000..4e63e3b7
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter21.ipynb
@@ -0,0 +1,106 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:42eb4bd0fae1331d52fd855bad43219acea712dc31c5270f1f64fa698ba366ad"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "21: Elementary particles"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 21.1, Page number 399"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mpi=140;     #mass of pi-meson\n",
+      "mp=938.3;    #mass of proton\n",
+      "mk=498;   #mass of k\n",
+      "m=1116;  \n",
+      "\n",
+      "#Calculation\n",
+      "Q=mpi+mp-mk-m;    #Q-value(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"Q-value is\",round(Q),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "Q-value is -536.0 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 21.2, Page number 399"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mpc2=938.3;    #energy of proton(MeV)\n",
+      "Epic2=139.6;   #energy of pi-meson(MeV)\n",
+      "mnc2=939.6;    #energy of neutron(MeV)\n",
+      "KE=0.6;    #kinetic energy of neutron(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Epi=mpc2+Epic2-mnc2-KE;    #energy conservation(MeV)\n",
+      "mpic2=math.sqrt((Epi**2)-((mnc2+KE)**2)+(mnc2**2));   #pi0 mass(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"pi0 mass is\",round(mpic2,1),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "pi0 mass is 133.5 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter21_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter21_1.ipynb
new file mode 100755
index 00000000..4e63e3b7
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter21_1.ipynb
@@ -0,0 +1,106 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:42eb4bd0fae1331d52fd855bad43219acea712dc31c5270f1f64fa698ba366ad"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "21: Elementary particles"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 21.1, Page number 399"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mpi=140;     #mass of pi-meson\n",
+      "mp=938.3;    #mass of proton\n",
+      "mk=498;   #mass of k\n",
+      "m=1116;  \n",
+      "\n",
+      "#Calculation\n",
+      "Q=mpi+mp-mk-m;    #Q-value(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"Q-value is\",round(Q),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "Q-value is -536.0 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 21.2, Page number 399"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mpc2=938.3;    #energy of proton(MeV)\n",
+      "Epic2=139.6;   #energy of pi-meson(MeV)\n",
+      "mnc2=939.6;    #energy of neutron(MeV)\n",
+      "KE=0.6;    #kinetic energy of neutron(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Epi=mpc2+Epic2-mnc2-KE;    #energy conservation(MeV)\n",
+      "mpic2=math.sqrt((Epi**2)-((mnc2+KE)**2)+(mnc2**2));   #pi0 mass(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"pi0 mass is\",round(mpic2,1),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "pi0 mass is 133.5 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter21_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter21_2.ipynb
new file mode 100755
index 00000000..4e63e3b7
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter21_2.ipynb
@@ -0,0 +1,106 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:42eb4bd0fae1331d52fd855bad43219acea712dc31c5270f1f64fa698ba366ad"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "21: Elementary particles"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 21.1, Page number 399"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mpi=140;     #mass of pi-meson\n",
+      "mp=938.3;    #mass of proton\n",
+      "mk=498;   #mass of k\n",
+      "m=1116;  \n",
+      "\n",
+      "#Calculation\n",
+      "Q=mpi+mp-mk-m;    #Q-value(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"Q-value is\",round(Q),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "Q-value is -536.0 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 21.2, Page number 399"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mpc2=938.3;    #energy of proton(MeV)\n",
+      "Epic2=139.6;   #energy of pi-meson(MeV)\n",
+      "mnc2=939.6;    #energy of neutron(MeV)\n",
+      "KE=0.6;    #kinetic energy of neutron(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Epi=mpc2+Epic2-mnc2-KE;    #energy conservation(MeV)\n",
+      "mpic2=math.sqrt((Epi**2)-((mnc2+KE)**2)+(mnc2**2));   #pi0 mass(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"pi0 mass is\",round(mpic2,1),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "pi0 mass is 133.5 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter21_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter21_3.ipynb
new file mode 100755
index 00000000..4e63e3b7
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter21_3.ipynb
@@ -0,0 +1,106 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:42eb4bd0fae1331d52fd855bad43219acea712dc31c5270f1f64fa698ba366ad"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "21: Elementary particles"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 21.1, Page number 399"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mpi=140;     #mass of pi-meson\n",
+      "mp=938.3;    #mass of proton\n",
+      "mk=498;   #mass of k\n",
+      "m=1116;  \n",
+      "\n",
+      "#Calculation\n",
+      "Q=mpi+mp-mk-m;    #Q-value(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"Q-value is\",round(Q),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "Q-value is -536.0 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 21.2, Page number 399"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mpc2=938.3;    #energy of proton(MeV)\n",
+      "Epic2=139.6;   #energy of pi-meson(MeV)\n",
+      "mnc2=939.6;    #energy of neutron(MeV)\n",
+      "KE=0.6;    #kinetic energy of neutron(MeV)\n",
+      "\n",
+      "#Calculation\n",
+      "Epi=mpc2+Epic2-mnc2-KE;    #energy conservation(MeV)\n",
+      "mpic2=math.sqrt((Epi**2)-((mnc2+KE)**2)+(mnc2**2));   #pi0 mass(MeV)\n",
+      "\n",
+      "#Result\n",
+      "print \"pi0 mass is\",round(mpic2,1),\"MeV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "pi0 mass is 133.5 MeV\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter2_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter2_1.ipynb
new file mode 100755
index 00000000..59d9ea57
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter2_1.ipynb
@@ -0,0 +1,295 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:f048d58df41f2578c151ef59f03652004b6758b9e666d170255be2c66115bfe2"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "2: Particle nature of radiation"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.1, Page number 28"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "new=100*10**6;    #frequency(Hz)\n",
+      "P=100*10**3;    #power(watt)\n",
+      "\n",
+      "#Calculation\n",
+      "E=h*new;    #quantum of energy(J)\n",
+      "n=P/E;    #number of quanta emitted(per sec)\n",
+      "\n",
+      "#Result\n",
+      "print \"number of quanta emitted is\",round(n/10**29,2),\"*10**29 per sec\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "number of quanta emitted is 15.09 *10**29 per sec\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.2, Page number 31"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=400*10**-9;    #wavelength(m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "w0=2.28;    #work function(eV)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "E=h*c/(lamda*e);    #energy(eV)\n",
+      "KEmax=E-w0;    #maximum kinetic energy(eV)\n",
+      "v2=2*KEmax*e/m;  \n",
+      "v=math.sqrt(v2);   #velocity(m/s)\n",
+      "\n",
+      "#Result\n",
+      "print \"maximum kinetic energy is\",round(KEmax,3),\"eV\"\n",
+      "print \"velocity of photoelectrons is\",round(v/10**5,2),\"*10**5 m/s\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "maximum kinetic energy is 0.826 eV\n",
+        "velocity of photoelectrons is 5.39 *10**5 m/s\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.3, Page number 31"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=2000*10**-10;    #wavelength(m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "w0=4.2;    #work function(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "lamda0=h*c/(w0*e);   #cut off wavelength(m)\n",
+      "E=h*c/(lamda*e);    #energy(eV)\n",
+      "sp=E-w0;    #stopping potential(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"cut off wavelength is\",int(lamda0*10**10),\"angstrom\"\n",
+      "print \"stopping potential is\",round(sp,2),\"V\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "cut off wavelength is 2958 angstrom\n",
+        "stopping potential is 2.01 V\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.4, Page number 33"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=0.2*10**-9;    #wavelength(m)\n",
+      "\n",
+      "#Calculation\n",
+      "p=h/lamda;    #momentum(kg m/s)\n",
+      "m=p/c;   #effective mass(kg)\n",
+      "\n",
+      "#Result\n",
+      "print \"momentum is\",round(p*10**24,1),\"*10**-24 kg m/s\"\n",
+      "print \"effective mass is\",round(m*10**32,1),\"*10**-32 kg\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "momentum is 3.3 *10**-24 kg m/s\n",
+        "effective mass is 1.1 *10**-32 kg\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.5, Page number 35"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=0.15;    #wavelength(nm)\n",
+      "m0=9.1*10**-31;    #mass of electron(kg)\n",
+      "theta1=0;   #scattering angle1(degrees)\n",
+      "theta2=90;   #scattering angle2(degrees)\n",
+      "theta3=180;   #scattering angle3(degrees)\n",
+      "\n",
+      "#Calculation\n",
+      "theta1=theta1*math.pi/180;   #scattering angle1(radian)\n",
+      "theta2=theta2*math.pi/180;   #scattering angle2(radian)\n",
+      "theta3=theta3*math.pi/180;   #scattering angle3(radian)\n",
+      "lamda_dash1=lamda+(h*(1-math.cos(theta1))/(m0*c));   #wavelength at 0(nm)\n",
+      "lamda_dash2=lamda+(10**9*h*(1-math.cos(theta2))/(m0*c));   #wavelength at 90(nm)\n",
+      "lamda_dash3=lamda+(10**9*h*(1-math.cos(theta3))/(m0*c));   #wavelength at 180(nm)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength at 0 degrees is\",lamda_dash1,\"nm\"\n",
+      "print \"wavelength at 90 degrees is\",round(lamda_dash2,3),\"nm\"\n",
+      "print \"wavelength at 180 degrees is\",round(lamda_dash3,3),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength at 0 degrees is 0.15 nm\n",
+        "wavelength at 90 degrees is 0.152 nm\n",
+        "wavelength at 180 degrees is 0.155 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 18
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.6, Page number 36"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "E=2*0.511*10**6;   #rest energy(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "lamda=h*c/(E*e);    #wavelength of photon(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength of photon is\",round(lamda*10**12,2),\"*10**-12 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength of photon is 1.22 *10**-12 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 21
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter2_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter2_2.ipynb
new file mode 100755
index 00000000..59d9ea57
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter2_2.ipynb
@@ -0,0 +1,295 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:f048d58df41f2578c151ef59f03652004b6758b9e666d170255be2c66115bfe2"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "2: Particle nature of radiation"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.1, Page number 28"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "new=100*10**6;    #frequency(Hz)\n",
+      "P=100*10**3;    #power(watt)\n",
+      "\n",
+      "#Calculation\n",
+      "E=h*new;    #quantum of energy(J)\n",
+      "n=P/E;    #number of quanta emitted(per sec)\n",
+      "\n",
+      "#Result\n",
+      "print \"number of quanta emitted is\",round(n/10**29,2),\"*10**29 per sec\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "number of quanta emitted is 15.09 *10**29 per sec\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.2, Page number 31"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=400*10**-9;    #wavelength(m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "w0=2.28;    #work function(eV)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "E=h*c/(lamda*e);    #energy(eV)\n",
+      "KEmax=E-w0;    #maximum kinetic energy(eV)\n",
+      "v2=2*KEmax*e/m;  \n",
+      "v=math.sqrt(v2);   #velocity(m/s)\n",
+      "\n",
+      "#Result\n",
+      "print \"maximum kinetic energy is\",round(KEmax,3),\"eV\"\n",
+      "print \"velocity of photoelectrons is\",round(v/10**5,2),\"*10**5 m/s\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "maximum kinetic energy is 0.826 eV\n",
+        "velocity of photoelectrons is 5.39 *10**5 m/s\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.3, Page number 31"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=2000*10**-10;    #wavelength(m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "w0=4.2;    #work function(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "lamda0=h*c/(w0*e);   #cut off wavelength(m)\n",
+      "E=h*c/(lamda*e);    #energy(eV)\n",
+      "sp=E-w0;    #stopping potential(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"cut off wavelength is\",int(lamda0*10**10),\"angstrom\"\n",
+      "print \"stopping potential is\",round(sp,2),\"V\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "cut off wavelength is 2958 angstrom\n",
+        "stopping potential is 2.01 V\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.4, Page number 33"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=0.2*10**-9;    #wavelength(m)\n",
+      "\n",
+      "#Calculation\n",
+      "p=h/lamda;    #momentum(kg m/s)\n",
+      "m=p/c;   #effective mass(kg)\n",
+      "\n",
+      "#Result\n",
+      "print \"momentum is\",round(p*10**24,1),\"*10**-24 kg m/s\"\n",
+      "print \"effective mass is\",round(m*10**32,1),\"*10**-32 kg\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "momentum is 3.3 *10**-24 kg m/s\n",
+        "effective mass is 1.1 *10**-32 kg\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.5, Page number 35"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=0.15;    #wavelength(nm)\n",
+      "m0=9.1*10**-31;    #mass of electron(kg)\n",
+      "theta1=0;   #scattering angle1(degrees)\n",
+      "theta2=90;   #scattering angle2(degrees)\n",
+      "theta3=180;   #scattering angle3(degrees)\n",
+      "\n",
+      "#Calculation\n",
+      "theta1=theta1*math.pi/180;   #scattering angle1(radian)\n",
+      "theta2=theta2*math.pi/180;   #scattering angle2(radian)\n",
+      "theta3=theta3*math.pi/180;   #scattering angle3(radian)\n",
+      "lamda_dash1=lamda+(h*(1-math.cos(theta1))/(m0*c));   #wavelength at 0(nm)\n",
+      "lamda_dash2=lamda+(10**9*h*(1-math.cos(theta2))/(m0*c));   #wavelength at 90(nm)\n",
+      "lamda_dash3=lamda+(10**9*h*(1-math.cos(theta3))/(m0*c));   #wavelength at 180(nm)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength at 0 degrees is\",lamda_dash1,\"nm\"\n",
+      "print \"wavelength at 90 degrees is\",round(lamda_dash2,3),\"nm\"\n",
+      "print \"wavelength at 180 degrees is\",round(lamda_dash3,3),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength at 0 degrees is 0.15 nm\n",
+        "wavelength at 90 degrees is 0.152 nm\n",
+        "wavelength at 180 degrees is 0.155 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 18
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.6, Page number 36"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "E=2*0.511*10**6;   #rest energy(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "lamda=h*c/(E*e);    #wavelength of photon(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength of photon is\",round(lamda*10**12,2),\"*10**-12 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength of photon is 1.22 *10**-12 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 21
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter2_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter2_3.ipynb
new file mode 100755
index 00000000..59d9ea57
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter2_3.ipynb
@@ -0,0 +1,295 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:f048d58df41f2578c151ef59f03652004b6758b9e666d170255be2c66115bfe2"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "2: Particle nature of radiation"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.1, Page number 28"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "new=100*10**6;    #frequency(Hz)\n",
+      "P=100*10**3;    #power(watt)\n",
+      "\n",
+      "#Calculation\n",
+      "E=h*new;    #quantum of energy(J)\n",
+      "n=P/E;    #number of quanta emitted(per sec)\n",
+      "\n",
+      "#Result\n",
+      "print \"number of quanta emitted is\",round(n/10**29,2),\"*10**29 per sec\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "number of quanta emitted is 15.09 *10**29 per sec\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.2, Page number 31"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=400*10**-9;    #wavelength(m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "w0=2.28;    #work function(eV)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "E=h*c/(lamda*e);    #energy(eV)\n",
+      "KEmax=E-w0;    #maximum kinetic energy(eV)\n",
+      "v2=2*KEmax*e/m;  \n",
+      "v=math.sqrt(v2);   #velocity(m/s)\n",
+      "\n",
+      "#Result\n",
+      "print \"maximum kinetic energy is\",round(KEmax,3),\"eV\"\n",
+      "print \"velocity of photoelectrons is\",round(v/10**5,2),\"*10**5 m/s\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "maximum kinetic energy is 0.826 eV\n",
+        "velocity of photoelectrons is 5.39 *10**5 m/s\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.3, Page number 31"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=2000*10**-10;    #wavelength(m)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "w0=4.2;    #work function(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "lamda0=h*c/(w0*e);   #cut off wavelength(m)\n",
+      "E=h*c/(lamda*e);    #energy(eV)\n",
+      "sp=E-w0;    #stopping potential(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"cut off wavelength is\",int(lamda0*10**10),\"angstrom\"\n",
+      "print \"stopping potential is\",round(sp,2),\"V\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "cut off wavelength is 2958 angstrom\n",
+        "stopping potential is 2.01 V\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.4, Page number 33"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=0.2*10**-9;    #wavelength(m)\n",
+      "\n",
+      "#Calculation\n",
+      "p=h/lamda;    #momentum(kg m/s)\n",
+      "m=p/c;   #effective mass(kg)\n",
+      "\n",
+      "#Result\n",
+      "print \"momentum is\",round(p*10**24,1),\"*10**-24 kg m/s\"\n",
+      "print \"effective mass is\",round(m*10**32,1),\"*10**-32 kg\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "momentum is 3.3 *10**-24 kg m/s\n",
+        "effective mass is 1.1 *10**-32 kg\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.5, Page number 35"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=0.15;    #wavelength(nm)\n",
+      "m0=9.1*10**-31;    #mass of electron(kg)\n",
+      "theta1=0;   #scattering angle1(degrees)\n",
+      "theta2=90;   #scattering angle2(degrees)\n",
+      "theta3=180;   #scattering angle3(degrees)\n",
+      "\n",
+      "#Calculation\n",
+      "theta1=theta1*math.pi/180;   #scattering angle1(radian)\n",
+      "theta2=theta2*math.pi/180;   #scattering angle2(radian)\n",
+      "theta3=theta3*math.pi/180;   #scattering angle3(radian)\n",
+      "lamda_dash1=lamda+(h*(1-math.cos(theta1))/(m0*c));   #wavelength at 0(nm)\n",
+      "lamda_dash2=lamda+(10**9*h*(1-math.cos(theta2))/(m0*c));   #wavelength at 90(nm)\n",
+      "lamda_dash3=lamda+(10**9*h*(1-math.cos(theta3))/(m0*c));   #wavelength at 180(nm)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength at 0 degrees is\",lamda_dash1,\"nm\"\n",
+      "print \"wavelength at 90 degrees is\",round(lamda_dash2,3),\"nm\"\n",
+      "print \"wavelength at 180 degrees is\",round(lamda_dash3,3),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength at 0 degrees is 0.15 nm\n",
+        "wavelength at 90 degrees is 0.152 nm\n",
+        "wavelength at 180 degrees is 0.155 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 18
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 2.6, Page number 36"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "E=2*0.511*10**6;   #rest energy(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "lamda=h*c/(E*e);    #wavelength of photon(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength of photon is\",round(lamda*10**12,2),\"*10**-12 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength of photon is 1.22 *10**-12 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 21
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter3.ipynb
new file mode 100755
index 00000000..4d816cd2
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter3.ipynb
@@ -0,0 +1,197 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:b6d6dfa593701249cd6d305eb45cecde030c3502c19d325045b7e05cf46a035c"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "3: Atomic models"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 3.1, Page number 45"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "N=6.02*10**23;    #avagadro number(atoms/mole)\n",
+      "rho=19.3;   #density(g/cc)\n",
+      "A=197;   #atomic weight(g)\n",
+      "k=8.984*10**9;  #value of k(Nm**2/C**2)\n",
+      "Z=79;\n",
+      "Zdash=2;\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=2;\n",
+      "v0=8*10**6;  \n",
+      "t=2*10**-6;   #thickness(m)\n",
+      "\n",
+      "#Calculation\n",
+      "n=N*rho*10**6/A;    #number of atoms(per m**3)\n",
+      "b=k*Z*Zdash*e/(m*v0);   #impact parameter(m)\n",
+      "f=math.pi*b**2*n*t;    #fraction of particles scattered\n",
+      "\n",
+      "#Result\n",
+      "print \"fraction of particles scattered is\",round(f*10**5,1),\"*10**-5\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "fraction of particles scattered is 7.5 *10**-5\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 3.3, Page number 48"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "E=10.5;   #energy(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "E=(13.6+E)*e;   #energy of photon(J)\n",
+      "lamda=h*c/E;   #wavelength(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength of photon is\",round(lamda*10**9,2),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength of photon is 51.55 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 3.4, Page number 49"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "k=8.98*10**9;  #value of k(Nm**2/C**2)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "n=1;  #assume\n",
+      "a0=0.53*10**-10;    #radius of orbit(m)\n",
+      "\n",
+      "#Calculation\n",
+      "PE=-k*(e**2)/(a0*e*n**2);   #potential energy(eV)\n",
+      "E=-13.6/n**2;   #energy(eV)\n",
+      "KE=E-PE;   #kinetic energy(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"kinetic energy is\",round(KE,1),\"/n**2 eV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "kinetic energy is 13.5 /n**2 eV\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 3.6, Page number 51"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "Mbyme=1836;    \n",
+      "lamda=6562.8;    #wavelength for hydrogen(angstrom)\n",
+      "\n",
+      "#Calculation\n",
+      "mew_dashbymew=2*(1+Mbyme)/(1+(2*Mbyme));\n",
+      "lamda_dash=lamda/mew_dashbymew;    #wavelength for deuterium(angstrom)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength for deuterium is\",int(lamda_dash),\"angstrom\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength for deuterium is 6561 angstrom\n"
+       ]
+      }
+     ],
+     "prompt_number": 14
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter3_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter3_1.ipynb
new file mode 100755
index 00000000..4d816cd2
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter3_1.ipynb
@@ -0,0 +1,197 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:b6d6dfa593701249cd6d305eb45cecde030c3502c19d325045b7e05cf46a035c"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "3: Atomic models"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 3.1, Page number 45"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "N=6.02*10**23;    #avagadro number(atoms/mole)\n",
+      "rho=19.3;   #density(g/cc)\n",
+      "A=197;   #atomic weight(g)\n",
+      "k=8.984*10**9;  #value of k(Nm**2/C**2)\n",
+      "Z=79;\n",
+      "Zdash=2;\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=2;\n",
+      "v0=8*10**6;  \n",
+      "t=2*10**-6;   #thickness(m)\n",
+      "\n",
+      "#Calculation\n",
+      "n=N*rho*10**6/A;    #number of atoms(per m**3)\n",
+      "b=k*Z*Zdash*e/(m*v0);   #impact parameter(m)\n",
+      "f=math.pi*b**2*n*t;    #fraction of particles scattered\n",
+      "\n",
+      "#Result\n",
+      "print \"fraction of particles scattered is\",round(f*10**5,1),\"*10**-5\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "fraction of particles scattered is 7.5 *10**-5\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 3.3, Page number 48"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "E=10.5;   #energy(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "E=(13.6+E)*e;   #energy of photon(J)\n",
+      "lamda=h*c/E;   #wavelength(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength of photon is\",round(lamda*10**9,2),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength of photon is 51.55 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 3.4, Page number 49"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "k=8.98*10**9;  #value of k(Nm**2/C**2)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "n=1;  #assume\n",
+      "a0=0.53*10**-10;    #radius of orbit(m)\n",
+      "\n",
+      "#Calculation\n",
+      "PE=-k*(e**2)/(a0*e*n**2);   #potential energy(eV)\n",
+      "E=-13.6/n**2;   #energy(eV)\n",
+      "KE=E-PE;   #kinetic energy(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"kinetic energy is\",round(KE,1),\"/n**2 eV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "kinetic energy is 13.5 /n**2 eV\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 3.6, Page number 51"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "Mbyme=1836;    \n",
+      "lamda=6562.8;    #wavelength for hydrogen(angstrom)\n",
+      "\n",
+      "#Calculation\n",
+      "mew_dashbymew=2*(1+Mbyme)/(1+(2*Mbyme));\n",
+      "lamda_dash=lamda/mew_dashbymew;    #wavelength for deuterium(angstrom)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength for deuterium is\",int(lamda_dash),\"angstrom\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength for deuterium is 6561 angstrom\n"
+       ]
+      }
+     ],
+     "prompt_number": 14
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter3_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter3_2.ipynb
new file mode 100755
index 00000000..4d816cd2
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter3_2.ipynb
@@ -0,0 +1,197 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:b6d6dfa593701249cd6d305eb45cecde030c3502c19d325045b7e05cf46a035c"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "3: Atomic models"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 3.1, Page number 45"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "N=6.02*10**23;    #avagadro number(atoms/mole)\n",
+      "rho=19.3;   #density(g/cc)\n",
+      "A=197;   #atomic weight(g)\n",
+      "k=8.984*10**9;  #value of k(Nm**2/C**2)\n",
+      "Z=79;\n",
+      "Zdash=2;\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=2;\n",
+      "v0=8*10**6;  \n",
+      "t=2*10**-6;   #thickness(m)\n",
+      "\n",
+      "#Calculation\n",
+      "n=N*rho*10**6/A;    #number of atoms(per m**3)\n",
+      "b=k*Z*Zdash*e/(m*v0);   #impact parameter(m)\n",
+      "f=math.pi*b**2*n*t;    #fraction of particles scattered\n",
+      "\n",
+      "#Result\n",
+      "print \"fraction of particles scattered is\",round(f*10**5,1),\"*10**-5\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "fraction of particles scattered is 7.5 *10**-5\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 3.3, Page number 48"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "E=10.5;   #energy(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "E=(13.6+E)*e;   #energy of photon(J)\n",
+      "lamda=h*c/E;   #wavelength(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength of photon is\",round(lamda*10**9,2),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength of photon is 51.55 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 3.4, Page number 49"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "k=8.98*10**9;  #value of k(Nm**2/C**2)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "n=1;  #assume\n",
+      "a0=0.53*10**-10;    #radius of orbit(m)\n",
+      "\n",
+      "#Calculation\n",
+      "PE=-k*(e**2)/(a0*e*n**2);   #potential energy(eV)\n",
+      "E=-13.6/n**2;   #energy(eV)\n",
+      "KE=E-PE;   #kinetic energy(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"kinetic energy is\",round(KE,1),\"/n**2 eV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "kinetic energy is 13.5 /n**2 eV\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 3.6, Page number 51"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "Mbyme=1836;    \n",
+      "lamda=6562.8;    #wavelength for hydrogen(angstrom)\n",
+      "\n",
+      "#Calculation\n",
+      "mew_dashbymew=2*(1+Mbyme)/(1+(2*Mbyme));\n",
+      "lamda_dash=lamda/mew_dashbymew;    #wavelength for deuterium(angstrom)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength for deuterium is\",int(lamda_dash),\"angstrom\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength for deuterium is 6561 angstrom\n"
+       ]
+      }
+     ],
+     "prompt_number": 14
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter3_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter3_3.ipynb
new file mode 100755
index 00000000..4d816cd2
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter3_3.ipynb
@@ -0,0 +1,197 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:b6d6dfa593701249cd6d305eb45cecde030c3502c19d325045b7e05cf46a035c"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "3: Atomic models"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 3.1, Page number 45"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "N=6.02*10**23;    #avagadro number(atoms/mole)\n",
+      "rho=19.3;   #density(g/cc)\n",
+      "A=197;   #atomic weight(g)\n",
+      "k=8.984*10**9;  #value of k(Nm**2/C**2)\n",
+      "Z=79;\n",
+      "Zdash=2;\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=2;\n",
+      "v0=8*10**6;  \n",
+      "t=2*10**-6;   #thickness(m)\n",
+      "\n",
+      "#Calculation\n",
+      "n=N*rho*10**6/A;    #number of atoms(per m**3)\n",
+      "b=k*Z*Zdash*e/(m*v0);   #impact parameter(m)\n",
+      "f=math.pi*b**2*n*t;    #fraction of particles scattered\n",
+      "\n",
+      "#Result\n",
+      "print \"fraction of particles scattered is\",round(f*10**5,1),\"*10**-5\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "fraction of particles scattered is 7.5 *10**-5\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 3.3, Page number 48"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "E=10.5;   #energy(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "E=(13.6+E)*e;   #energy of photon(J)\n",
+      "lamda=h*c/E;   #wavelength(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength of photon is\",round(lamda*10**9,2),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength of photon is 51.55 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 3.4, Page number 49"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "k=8.98*10**9;  #value of k(Nm**2/C**2)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "n=1;  #assume\n",
+      "a0=0.53*10**-10;    #radius of orbit(m)\n",
+      "\n",
+      "#Calculation\n",
+      "PE=-k*(e**2)/(a0*e*n**2);   #potential energy(eV)\n",
+      "E=-13.6/n**2;   #energy(eV)\n",
+      "KE=E-PE;   #kinetic energy(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"kinetic energy is\",round(KE,1),\"/n**2 eV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "kinetic energy is 13.5 /n**2 eV\n"
+       ]
+      }
+     ],
+     "prompt_number": 11
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 3.6, Page number 51"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "Mbyme=1836;    \n",
+      "lamda=6562.8;    #wavelength for hydrogen(angstrom)\n",
+      "\n",
+      "#Calculation\n",
+      "mew_dashbymew=2*(1+Mbyme)/(1+(2*Mbyme));\n",
+      "lamda_dash=lamda/mew_dashbymew;    #wavelength for deuterium(angstrom)\n",
+      "\n",
+      "#Result\n",
+      "print \"wavelength for deuterium is\",int(lamda_dash),\"angstrom\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "wavelength for deuterium is 6561 angstrom\n"
+       ]
+      }
+     ],
+     "prompt_number": 14
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter4.ipynb b/Modern_Physics_By_G.Aruldas/Chapter4.ipynb
new file mode 100755
index 00000000..350acf21
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter4.ipynb
@@ -0,0 +1,193 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:1d6457e2a94e0fa2b026a0acb8ba4fab526573258ee2c274c4328b7f611fb97a"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "4: Wave mechanical concepts"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 4.1, Page number 59"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "V=1;    #assume\n",
+      "\n",
+      "#Calculation\n",
+      "lamda=h/math.sqrt(2*m*e*V);    #debroglie wavelength(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"debroglie wavelength is math.sqrt(\",int((lamda*10**10)**2),\"/V) angstrom\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "debroglie wavelength is math.sqrt( 150 /V) angstrom\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 4.2, Page number 59"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "KE=100*10**6;   #kinetic energy(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "p=math.sqrt(2*m*e);     #momentum(kg m/s)\n",
+      "lamda1=h/p;    #debroglie wavelength for 1 eV(m)\n",
+      "lamda2=h*c/(KE*e);    #debroglie wavelength for 100 MeV(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"debroglie wavelength for 1 eV is\",round(lamda1*10**9,1),\"nm\"\n",
+      "print \"debroglie wavelength for 100 MeV is\",round(lamda2*10**15,2),\"*10**-15 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "debroglie wavelength for 1 eV is 1.2 nm\n",
+        "debroglie wavelength for 100 MeV is 12.42 *10**-15 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 4.3, Page number 64"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "v=4*10**6;    #speed of electron(m/s)\n",
+      "sp=1/100;     #speed precision\n",
+      "hbar=1.05*10**-34;  \n",
+      "\n",
+      "#Calculation\n",
+      "p=m*v;   #momentum(kg m/s)\n",
+      "deltap=p*sp;    #uncertainity in momentum(kg m/s)\n",
+      "deltax=hbar/(2*deltap);   #precision in position(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"precision in position is\",round(deltax*10**9,2),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "precision in position is 1.44 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 14
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 4.4, Page number 64"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=4000*10**-10;    #wavelength(m)\n",
+      "deltat=10**-8;    #average lifetime(s)\n",
+      "\n",
+      "#Calculation\n",
+      "delta_lamda=lamda**2/(4*math.pi*c*deltat);   #width of line(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"width of line is\",round(delta_lamda*10**15,2),\"*10**-15 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "width of line is 4.24 *10**-15 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 16
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter4_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter4_1.ipynb
new file mode 100755
index 00000000..350acf21
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter4_1.ipynb
@@ -0,0 +1,193 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:1d6457e2a94e0fa2b026a0acb8ba4fab526573258ee2c274c4328b7f611fb97a"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "4: Wave mechanical concepts"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 4.1, Page number 59"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "V=1;    #assume\n",
+      "\n",
+      "#Calculation\n",
+      "lamda=h/math.sqrt(2*m*e*V);    #debroglie wavelength(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"debroglie wavelength is math.sqrt(\",int((lamda*10**10)**2),\"/V) angstrom\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "debroglie wavelength is math.sqrt( 150 /V) angstrom\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 4.2, Page number 59"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "KE=100*10**6;   #kinetic energy(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "p=math.sqrt(2*m*e);     #momentum(kg m/s)\n",
+      "lamda1=h/p;    #debroglie wavelength for 1 eV(m)\n",
+      "lamda2=h*c/(KE*e);    #debroglie wavelength for 100 MeV(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"debroglie wavelength for 1 eV is\",round(lamda1*10**9,1),\"nm\"\n",
+      "print \"debroglie wavelength for 100 MeV is\",round(lamda2*10**15,2),\"*10**-15 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "debroglie wavelength for 1 eV is 1.2 nm\n",
+        "debroglie wavelength for 100 MeV is 12.42 *10**-15 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 4.3, Page number 64"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "v=4*10**6;    #speed of electron(m/s)\n",
+      "sp=1/100;     #speed precision\n",
+      "hbar=1.05*10**-34;  \n",
+      "\n",
+      "#Calculation\n",
+      "p=m*v;   #momentum(kg m/s)\n",
+      "deltap=p*sp;    #uncertainity in momentum(kg m/s)\n",
+      "deltax=hbar/(2*deltap);   #precision in position(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"precision in position is\",round(deltax*10**9,2),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "precision in position is 1.44 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 14
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 4.4, Page number 64"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=4000*10**-10;    #wavelength(m)\n",
+      "deltat=10**-8;    #average lifetime(s)\n",
+      "\n",
+      "#Calculation\n",
+      "delta_lamda=lamda**2/(4*math.pi*c*deltat);   #width of line(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"width of line is\",round(delta_lamda*10**15,2),\"*10**-15 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "width of line is 4.24 *10**-15 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 16
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter4_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter4_2.ipynb
new file mode 100755
index 00000000..350acf21
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter4_2.ipynb
@@ -0,0 +1,193 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:1d6457e2a94e0fa2b026a0acb8ba4fab526573258ee2c274c4328b7f611fb97a"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "4: Wave mechanical concepts"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 4.1, Page number 59"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "V=1;    #assume\n",
+      "\n",
+      "#Calculation\n",
+      "lamda=h/math.sqrt(2*m*e*V);    #debroglie wavelength(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"debroglie wavelength is math.sqrt(\",int((lamda*10**10)**2),\"/V) angstrom\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "debroglie wavelength is math.sqrt( 150 /V) angstrom\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 4.2, Page number 59"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "KE=100*10**6;   #kinetic energy(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "p=math.sqrt(2*m*e);     #momentum(kg m/s)\n",
+      "lamda1=h/p;    #debroglie wavelength for 1 eV(m)\n",
+      "lamda2=h*c/(KE*e);    #debroglie wavelength for 100 MeV(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"debroglie wavelength for 1 eV is\",round(lamda1*10**9,1),\"nm\"\n",
+      "print \"debroglie wavelength for 100 MeV is\",round(lamda2*10**15,2),\"*10**-15 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "debroglie wavelength for 1 eV is 1.2 nm\n",
+        "debroglie wavelength for 100 MeV is 12.42 *10**-15 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 4.3, Page number 64"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "v=4*10**6;    #speed of electron(m/s)\n",
+      "sp=1/100;     #speed precision\n",
+      "hbar=1.05*10**-34;  \n",
+      "\n",
+      "#Calculation\n",
+      "p=m*v;   #momentum(kg m/s)\n",
+      "deltap=p*sp;    #uncertainity in momentum(kg m/s)\n",
+      "deltax=hbar/(2*deltap);   #precision in position(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"precision in position is\",round(deltax*10**9,2),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "precision in position is 1.44 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 14
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 4.4, Page number 64"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=4000*10**-10;    #wavelength(m)\n",
+      "deltat=10**-8;    #average lifetime(s)\n",
+      "\n",
+      "#Calculation\n",
+      "delta_lamda=lamda**2/(4*math.pi*c*deltat);   #width of line(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"width of line is\",round(delta_lamda*10**15,2),\"*10**-15 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "width of line is 4.24 *10**-15 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 16
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter4_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter4_3.ipynb
new file mode 100755
index 00000000..350acf21
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter4_3.ipynb
@@ -0,0 +1,193 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:1d6457e2a94e0fa2b026a0acb8ba4fab526573258ee2c274c4328b7f611fb97a"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "4: Wave mechanical concepts"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 4.1, Page number 59"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "V=1;    #assume\n",
+      "\n",
+      "#Calculation\n",
+      "lamda=h/math.sqrt(2*m*e*V);    #debroglie wavelength(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"debroglie wavelength is math.sqrt(\",int((lamda*10**10)**2),\"/V) angstrom\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "debroglie wavelength is math.sqrt( 150 /V) angstrom\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 4.2, Page number 59"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "KE=100*10**6;   #kinetic energy(eV)\n",
+      "\n",
+      "#Calculation\n",
+      "p=math.sqrt(2*m*e);     #momentum(kg m/s)\n",
+      "lamda1=h/p;    #debroglie wavelength for 1 eV(m)\n",
+      "lamda2=h*c/(KE*e);    #debroglie wavelength for 100 MeV(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"debroglie wavelength for 1 eV is\",round(lamda1*10**9,1),\"nm\"\n",
+      "print \"debroglie wavelength for 100 MeV is\",round(lamda2*10**15,2),\"*10**-15 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "debroglie wavelength for 1 eV is 1.2 nm\n",
+        "debroglie wavelength for 100 MeV is 12.42 *10**-15 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 4.3, Page number 64"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "v=4*10**6;    #speed of electron(m/s)\n",
+      "sp=1/100;     #speed precision\n",
+      "hbar=1.05*10**-34;  \n",
+      "\n",
+      "#Calculation\n",
+      "p=m*v;   #momentum(kg m/s)\n",
+      "deltap=p*sp;    #uncertainity in momentum(kg m/s)\n",
+      "deltax=hbar/(2*deltap);   #precision in position(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"precision in position is\",round(deltax*10**9,2),\"nm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "precision in position is 1.44 nm\n"
+       ]
+      }
+     ],
+     "prompt_number": 14
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 4.4, Page number 64"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda=4000*10**-10;    #wavelength(m)\n",
+      "deltat=10**-8;    #average lifetime(s)\n",
+      "\n",
+      "#Calculation\n",
+      "delta_lamda=lamda**2/(4*math.pi*c*deltat);   #width of line(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"width of line is\",round(delta_lamda*10**15,2),\"*10**-15 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "width of line is 4.24 *10**-15 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 16
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter6.ipynb b/Modern_Physics_By_G.Aruldas/Chapter6.ipynb
new file mode 100755
index 00000000..fa8615c7
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter6.ipynb
@@ -0,0 +1,208 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:8884b20a8f08880d4a94501a9f3a466664f30ca1f04c541fe7d3a232f87a24bc"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "6: Quantum mechanics of simple systems"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 6.1, Page number 90"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from scipy.integrate import quad\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "a=2*10**-10;    #length of square well(m)\n",
+      "\n",
+      "#Calculation\n",
+      "def intg(x):\n",
+      "    return (2/a)*(math.sin(math.pi*x/a))**2\n",
+      "\n",
+      "S=quad(intg,0,0.25*10**-10)[0]     #probability of finding the electron\n",
+      "\n",
+      "#Result\n",
+      "print \"probability of finding the electron is\",round(S,4)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "probability of finding the electron is 0.0125\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 6.2, Page number 96"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "new0=6.43*10**13;   #frequency(Hz)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "mew=1.1385*10**-26;     #reduced mass(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "E0=h*new0/2;   #zero point energy(J)\n",
+      "E0=E0/e;   #zero point energy(eV)\n",
+      "k=4*math.pi**2*new0**2*mew;   #force constane(N/m)\n",
+      "\n",
+      "#Result\n",
+      "print \"zero point energy is\",round(E0,3),\"eV\"\n",
+      "print \"force constane is\",round(k),\"N/m\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "zero point energy is 0.133 eV\n",
+        "force constane is 1858.0 N/m\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 6.6, Page number 104"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m1=19.9217*10**-27;    #mass of carbon atom(kg)\n",
+      "m2=26.5614*10**-27;    #mass of oxygen atom(kg)\n",
+      "r=1.131*10**-10;   #separation(m)\n",
+      "hbar=1.054*10**-34;\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "mew=(m1*m2)/(m1+m2);    #reduced mass(kg)\n",
+      "I=mew*r**2;    \n",
+      "deltaE=hbar**2/I;    #energy difference(J)\n",
+      "deltaE=deltaE/e;     #energy difference(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy difference is\",round(deltaE*10**4,2),\"*10**-4 eV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy difference is 4.77 *10**-4 eV\n"
+       ]
+      }
+     ],
+     "prompt_number": 21
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 6.7, Page number 105"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m1=1;\n",
+      "m2=0;\n",
+      "m3=-1;     #m-components\n",
+      "l=1;\n",
+      "\n",
+      "#Calculation\n",
+      "L=math.sqrt(l*(l+1));    #length of vector\n",
+      "theta1=math.acos(m1/L);   #orientation for m=1(radian)\n",
+      "theta1=theta1*180/math.pi;   #orientation for m=1(degrees)\n",
+      "theta2=math.acos(m2/L);   #orientation for m=0(radian)\n",
+      "theta2=theta2*180/math.pi;   #orientation for m=0(degrees)\n",
+      "theta3=math.acos(m3/L);   #orientation for m=-1(radian)\n",
+      "theta3=theta3*180/math.pi;   #orientation for m=-1(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"orientation for m=1 is\",theta1,\"degrees\"\n",
+      "print \"orientation for m=0 is\",theta2,\"degrees\"\n",
+      "print \"orientation for m=-1 is\",theta3,\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "orientation for m=1 is 45.0 degrees\n",
+        "orientation for m=0 is 90.0 degrees\n",
+        "orientation for m=-1 is 135.0 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 22
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter6_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter6_1.ipynb
new file mode 100755
index 00000000..fa8615c7
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter6_1.ipynb
@@ -0,0 +1,208 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:8884b20a8f08880d4a94501a9f3a466664f30ca1f04c541fe7d3a232f87a24bc"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "6: Quantum mechanics of simple systems"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 6.1, Page number 90"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from scipy.integrate import quad\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "a=2*10**-10;    #length of square well(m)\n",
+      "\n",
+      "#Calculation\n",
+      "def intg(x):\n",
+      "    return (2/a)*(math.sin(math.pi*x/a))**2\n",
+      "\n",
+      "S=quad(intg,0,0.25*10**-10)[0]     #probability of finding the electron\n",
+      "\n",
+      "#Result\n",
+      "print \"probability of finding the electron is\",round(S,4)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "probability of finding the electron is 0.0125\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 6.2, Page number 96"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "new0=6.43*10**13;   #frequency(Hz)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "mew=1.1385*10**-26;     #reduced mass(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "E0=h*new0/2;   #zero point energy(J)\n",
+      "E0=E0/e;   #zero point energy(eV)\n",
+      "k=4*math.pi**2*new0**2*mew;   #force constane(N/m)\n",
+      "\n",
+      "#Result\n",
+      "print \"zero point energy is\",round(E0,3),\"eV\"\n",
+      "print \"force constane is\",round(k),\"N/m\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "zero point energy is 0.133 eV\n",
+        "force constane is 1858.0 N/m\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 6.6, Page number 104"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m1=19.9217*10**-27;    #mass of carbon atom(kg)\n",
+      "m2=26.5614*10**-27;    #mass of oxygen atom(kg)\n",
+      "r=1.131*10**-10;   #separation(m)\n",
+      "hbar=1.054*10**-34;\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "mew=(m1*m2)/(m1+m2);    #reduced mass(kg)\n",
+      "I=mew*r**2;    \n",
+      "deltaE=hbar**2/I;    #energy difference(J)\n",
+      "deltaE=deltaE/e;     #energy difference(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy difference is\",round(deltaE*10**4,2),\"*10**-4 eV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy difference is 4.77 *10**-4 eV\n"
+       ]
+      }
+     ],
+     "prompt_number": 21
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 6.7, Page number 105"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m1=1;\n",
+      "m2=0;\n",
+      "m3=-1;     #m-components\n",
+      "l=1;\n",
+      "\n",
+      "#Calculation\n",
+      "L=math.sqrt(l*(l+1));    #length of vector\n",
+      "theta1=math.acos(m1/L);   #orientation for m=1(radian)\n",
+      "theta1=theta1*180/math.pi;   #orientation for m=1(degrees)\n",
+      "theta2=math.acos(m2/L);   #orientation for m=0(radian)\n",
+      "theta2=theta2*180/math.pi;   #orientation for m=0(degrees)\n",
+      "theta3=math.acos(m3/L);   #orientation for m=-1(radian)\n",
+      "theta3=theta3*180/math.pi;   #orientation for m=-1(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"orientation for m=1 is\",theta1,\"degrees\"\n",
+      "print \"orientation for m=0 is\",theta2,\"degrees\"\n",
+      "print \"orientation for m=-1 is\",theta3,\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "orientation for m=1 is 45.0 degrees\n",
+        "orientation for m=0 is 90.0 degrees\n",
+        "orientation for m=-1 is 135.0 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 22
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter6_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter6_2.ipynb
new file mode 100755
index 00000000..fa8615c7
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter6_2.ipynb
@@ -0,0 +1,208 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:8884b20a8f08880d4a94501a9f3a466664f30ca1f04c541fe7d3a232f87a24bc"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "6: Quantum mechanics of simple systems"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 6.1, Page number 90"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from scipy.integrate import quad\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "a=2*10**-10;    #length of square well(m)\n",
+      "\n",
+      "#Calculation\n",
+      "def intg(x):\n",
+      "    return (2/a)*(math.sin(math.pi*x/a))**2\n",
+      "\n",
+      "S=quad(intg,0,0.25*10**-10)[0]     #probability of finding the electron\n",
+      "\n",
+      "#Result\n",
+      "print \"probability of finding the electron is\",round(S,4)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "probability of finding the electron is 0.0125\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 6.2, Page number 96"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "new0=6.43*10**13;   #frequency(Hz)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "mew=1.1385*10**-26;     #reduced mass(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "E0=h*new0/2;   #zero point energy(J)\n",
+      "E0=E0/e;   #zero point energy(eV)\n",
+      "k=4*math.pi**2*new0**2*mew;   #force constane(N/m)\n",
+      "\n",
+      "#Result\n",
+      "print \"zero point energy is\",round(E0,3),\"eV\"\n",
+      "print \"force constane is\",round(k),\"N/m\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "zero point energy is 0.133 eV\n",
+        "force constane is 1858.0 N/m\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 6.6, Page number 104"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m1=19.9217*10**-27;    #mass of carbon atom(kg)\n",
+      "m2=26.5614*10**-27;    #mass of oxygen atom(kg)\n",
+      "r=1.131*10**-10;   #separation(m)\n",
+      "hbar=1.054*10**-34;\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "mew=(m1*m2)/(m1+m2);    #reduced mass(kg)\n",
+      "I=mew*r**2;    \n",
+      "deltaE=hbar**2/I;    #energy difference(J)\n",
+      "deltaE=deltaE/e;     #energy difference(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy difference is\",round(deltaE*10**4,2),\"*10**-4 eV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy difference is 4.77 *10**-4 eV\n"
+       ]
+      }
+     ],
+     "prompt_number": 21
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 6.7, Page number 105"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m1=1;\n",
+      "m2=0;\n",
+      "m3=-1;     #m-components\n",
+      "l=1;\n",
+      "\n",
+      "#Calculation\n",
+      "L=math.sqrt(l*(l+1));    #length of vector\n",
+      "theta1=math.acos(m1/L);   #orientation for m=1(radian)\n",
+      "theta1=theta1*180/math.pi;   #orientation for m=1(degrees)\n",
+      "theta2=math.acos(m2/L);   #orientation for m=0(radian)\n",
+      "theta2=theta2*180/math.pi;   #orientation for m=0(degrees)\n",
+      "theta3=math.acos(m3/L);   #orientation for m=-1(radian)\n",
+      "theta3=theta3*180/math.pi;   #orientation for m=-1(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"orientation for m=1 is\",theta1,\"degrees\"\n",
+      "print \"orientation for m=0 is\",theta2,\"degrees\"\n",
+      "print \"orientation for m=-1 is\",theta3,\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "orientation for m=1 is 45.0 degrees\n",
+        "orientation for m=0 is 90.0 degrees\n",
+        "orientation for m=-1 is 135.0 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 22
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter6_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter6_3.ipynb
new file mode 100755
index 00000000..fa8615c7
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter6_3.ipynb
@@ -0,0 +1,208 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:8884b20a8f08880d4a94501a9f3a466664f30ca1f04c541fe7d3a232f87a24bc"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "6: Quantum mechanics of simple systems"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 6.1, Page number 90"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from scipy.integrate import quad\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "a=2*10**-10;    #length of square well(m)\n",
+      "\n",
+      "#Calculation\n",
+      "def intg(x):\n",
+      "    return (2/a)*(math.sin(math.pi*x/a))**2\n",
+      "\n",
+      "S=quad(intg,0,0.25*10**-10)[0]     #probability of finding the electron\n",
+      "\n",
+      "#Result\n",
+      "print \"probability of finding the electron is\",round(S,4)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "probability of finding the electron is 0.0125\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 6.2, Page number 96"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "new0=6.43*10**13;   #frequency(Hz)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "mew=1.1385*10**-26;     #reduced mass(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "E0=h*new0/2;   #zero point energy(J)\n",
+      "E0=E0/e;   #zero point energy(eV)\n",
+      "k=4*math.pi**2*new0**2*mew;   #force constane(N/m)\n",
+      "\n",
+      "#Result\n",
+      "print \"zero point energy is\",round(E0,3),\"eV\"\n",
+      "print \"force constane is\",round(k),\"N/m\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "zero point energy is 0.133 eV\n",
+        "force constane is 1858.0 N/m\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 6.6, Page number 104"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m1=19.9217*10**-27;    #mass of carbon atom(kg)\n",
+      "m2=26.5614*10**-27;    #mass of oxygen atom(kg)\n",
+      "r=1.131*10**-10;   #separation(m)\n",
+      "hbar=1.054*10**-34;\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "mew=(m1*m2)/(m1+m2);    #reduced mass(kg)\n",
+      "I=mew*r**2;    \n",
+      "deltaE=hbar**2/I;    #energy difference(J)\n",
+      "deltaE=deltaE/e;     #energy difference(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy difference is\",round(deltaE*10**4,2),\"*10**-4 eV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy difference is 4.77 *10**-4 eV\n"
+       ]
+      }
+     ],
+     "prompt_number": 21
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 6.7, Page number 105"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m1=1;\n",
+      "m2=0;\n",
+      "m3=-1;     #m-components\n",
+      "l=1;\n",
+      "\n",
+      "#Calculation\n",
+      "L=math.sqrt(l*(l+1));    #length of vector\n",
+      "theta1=math.acos(m1/L);   #orientation for m=1(radian)\n",
+      "theta1=theta1*180/math.pi;   #orientation for m=1(degrees)\n",
+      "theta2=math.acos(m2/L);   #orientation for m=0(radian)\n",
+      "theta2=theta2*180/math.pi;   #orientation for m=0(degrees)\n",
+      "theta3=math.acos(m3/L);   #orientation for m=-1(radian)\n",
+      "theta3=theta3*180/math.pi;   #orientation for m=-1(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"orientation for m=1 is\",theta1,\"degrees\"\n",
+      "print \"orientation for m=0 is\",theta2,\"degrees\"\n",
+      "print \"orientation for m=-1 is\",theta3,\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "orientation for m=1 is 45.0 degrees\n",
+        "orientation for m=0 is 90.0 degrees\n",
+        "orientation for m=-1 is 135.0 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 22
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter7.ipynb b/Modern_Physics_By_G.Aruldas/Chapter7.ipynb
new file mode 100755
index 00000000..45ed5766
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter7.ipynb
@@ -0,0 +1,258 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:1e02050388cdd15ca19e058c38c307c0fd0b145ef71769674c045940ea70b08b"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "7: Atomic physics"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.1, Page number 113"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mewB=9.27*10**-24;\n",
+      "B=3;   #magnetic field(T)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "E=2*mewB*B/e;    #energy difference(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy difference is\",round(E*10**4,2),\"*10**-4 eV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy difference is 3.48 *10**-4 eV\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.3, Page number 118"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "l=2;\n",
+      "s=1/2;\n",
+      "j1=2+(1/2);\n",
+      "j2=2-(1/2);\n",
+      "\n",
+      "#Calculation\n",
+      "L=math.sqrt(l*(l+1));   #value of L(hbar)\n",
+      "S=math.sqrt(s*(s+1));   #value of S(hbar)\n",
+      "J1=math.sqrt(j1*(j1+1));   #value of J for D5/2 state(hbar)\n",
+      "J2=math.sqrt(j2*(j2+1));   #value of J for D3/2 state(hbar)\n",
+      "costheta1=((j1*(j1+1))-(l*(l+1))-(s*(s+1)))/(2*L*S);\n",
+      "theta1=math.acos(costheta1);    #angle between L and S for D5/2(radian)\n",
+      "theta1=theta1*180/math.pi;    #angle between L and S for D5/2(degrees)\n",
+      "costheta2=((j2*(j2+1))-(l*(l+1))-(s*(s+1)))/(2*L*S);\n",
+      "theta2=math.acos(costheta2);    #angle between L and S for D3/2(radian)\n",
+      "theta2=theta2*180/math.pi;    #angle between L and S for D3/2(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"value of L is\",round(L,3),\"hbar\"\n",
+      "print \"value of S is\",round(S,3),\"hbar\"\n",
+      "print \"value of J for D5/2 state is\",round(J1,3),\"hbar\"\n",
+      "print \"value of J for D3/2 state is\",round(J2,3),\"hbar\"\n",
+      "print \"angle between L and S for D5/2 is\",round(theta1,2),\"degrees\"\n",
+      "print \"angle between L and S for D3/2 is\",int(theta2),\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "value of L is 2.449 hbar\n",
+        "value of S is 0.866 hbar\n",
+        "value of J for D5/2 state is 2.958 hbar\n",
+        "value of J for D3/2 state is 1.936 hbar\n",
+        "angle between L and S for D5/2 is 61.87 degrees\n",
+        "angle between L and S for D3/2 is 135 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 4
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.10, Page number 136"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "S=1;\n",
+      "L=1;  \n",
+      "J=1;\n",
+      "\n",
+      "#Calculation\n",
+      "a=L*(L+1)-(L*(L+1));\n",
+      "g1=1+(a/(2*L*(L+1)));    #lande's g-factor for pure orbital angular momentum\n",
+      "b=(S*(S+1)+(S*(S+1)))/(2*S*(S+1));   #lande's g-factor for pure spin angular momentum\n",
+      "g2=1+b;      #lande's g-factor for pure spin angular momentum\n",
+      "c=J*(J+1)+(S*(S+1))-(L*(L+1));\n",
+      "g3=1+(c/(2*J*(J+1)));   #lande's g-factor for state 3P1\n",
+      "\n",
+      "#Result\n",
+      "print \"lande's g-factor for pure orbital angular momentum is\",g1\n",
+      "print \"ande's g-factor for pure spin angular momentum is\",g2\n",
+      "print \"lande's g-factor for state 3P1 is\",g3"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "lande's g-factor for pure orbital angular momentum is 1.0\n",
+        "ande's g-factor for pure spin angular momentum is 2.0\n",
+        "lande's g-factor for state 3P1 is 1.5\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.12, Page number 141"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "EKalpha=21.99;   #energy in silver(keV)\n",
+      "EKbita=25.145;   #energy in silver(keV)\n",
+      "E=-25.514;    #energy of n=1 state(keV)\n",
+      " \n",
+      "#Calculation\n",
+      "ELalpha=EKbita-EKalpha;     #energy of L alpha X ray(keV)\n",
+      "E2=-E-EKalpha;    #binding energy of L electron(keV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy of L alpha X ray is\",ELalpha,\"keV\"\n",
+      "print \"binding energy of L electron is\",E2,\"keV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy of L alpha X ray is 3.155 keV\n",
+        "binding energy of L electron is 3.524 keV\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.13, Page number 141"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "Z=11;    #atomic number\n",
+      "R=1.097*10**7;    #value of R(per m)\n",
+      "\n",
+      "#Calculation\n",
+      "E=(3*h*c*R*(Z-1)**2)/4;     #energy of k aplha X-ray(keV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy of k aplha X-ray is\",round(E*10**16,2),\"*10**-16 keV\"\n",
+      "print \"answer given in the book is wrong\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy of k aplha X-ray is 1.64 *10**-16 keV\n",
+        "answer given in the book is wrong\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter7_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter7_1.ipynb
new file mode 100755
index 00000000..45ed5766
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter7_1.ipynb
@@ -0,0 +1,258 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:1e02050388cdd15ca19e058c38c307c0fd0b145ef71769674c045940ea70b08b"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "7: Atomic physics"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.1, Page number 113"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mewB=9.27*10**-24;\n",
+      "B=3;   #magnetic field(T)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "E=2*mewB*B/e;    #energy difference(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy difference is\",round(E*10**4,2),\"*10**-4 eV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy difference is 3.48 *10**-4 eV\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.3, Page number 118"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "l=2;\n",
+      "s=1/2;\n",
+      "j1=2+(1/2);\n",
+      "j2=2-(1/2);\n",
+      "\n",
+      "#Calculation\n",
+      "L=math.sqrt(l*(l+1));   #value of L(hbar)\n",
+      "S=math.sqrt(s*(s+1));   #value of S(hbar)\n",
+      "J1=math.sqrt(j1*(j1+1));   #value of J for D5/2 state(hbar)\n",
+      "J2=math.sqrt(j2*(j2+1));   #value of J for D3/2 state(hbar)\n",
+      "costheta1=((j1*(j1+1))-(l*(l+1))-(s*(s+1)))/(2*L*S);\n",
+      "theta1=math.acos(costheta1);    #angle between L and S for D5/2(radian)\n",
+      "theta1=theta1*180/math.pi;    #angle between L and S for D5/2(degrees)\n",
+      "costheta2=((j2*(j2+1))-(l*(l+1))-(s*(s+1)))/(2*L*S);\n",
+      "theta2=math.acos(costheta2);    #angle between L and S for D3/2(radian)\n",
+      "theta2=theta2*180/math.pi;    #angle between L and S for D3/2(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"value of L is\",round(L,3),\"hbar\"\n",
+      "print \"value of S is\",round(S,3),\"hbar\"\n",
+      "print \"value of J for D5/2 state is\",round(J1,3),\"hbar\"\n",
+      "print \"value of J for D3/2 state is\",round(J2,3),\"hbar\"\n",
+      "print \"angle between L and S for D5/2 is\",round(theta1,2),\"degrees\"\n",
+      "print \"angle between L and S for D3/2 is\",int(theta2),\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "value of L is 2.449 hbar\n",
+        "value of S is 0.866 hbar\n",
+        "value of J for D5/2 state is 2.958 hbar\n",
+        "value of J for D3/2 state is 1.936 hbar\n",
+        "angle between L and S for D5/2 is 61.87 degrees\n",
+        "angle between L and S for D3/2 is 135 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 4
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.10, Page number 136"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "S=1;\n",
+      "L=1;  \n",
+      "J=1;\n",
+      "\n",
+      "#Calculation\n",
+      "a=L*(L+1)-(L*(L+1));\n",
+      "g1=1+(a/(2*L*(L+1)));    #lande's g-factor for pure orbital angular momentum\n",
+      "b=(S*(S+1)+(S*(S+1)))/(2*S*(S+1));   #lande's g-factor for pure spin angular momentum\n",
+      "g2=1+b;      #lande's g-factor for pure spin angular momentum\n",
+      "c=J*(J+1)+(S*(S+1))-(L*(L+1));\n",
+      "g3=1+(c/(2*J*(J+1)));   #lande's g-factor for state 3P1\n",
+      "\n",
+      "#Result\n",
+      "print \"lande's g-factor for pure orbital angular momentum is\",g1\n",
+      "print \"ande's g-factor for pure spin angular momentum is\",g2\n",
+      "print \"lande's g-factor for state 3P1 is\",g3"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "lande's g-factor for pure orbital angular momentum is 1.0\n",
+        "ande's g-factor for pure spin angular momentum is 2.0\n",
+        "lande's g-factor for state 3P1 is 1.5\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.12, Page number 141"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "EKalpha=21.99;   #energy in silver(keV)\n",
+      "EKbita=25.145;   #energy in silver(keV)\n",
+      "E=-25.514;    #energy of n=1 state(keV)\n",
+      " \n",
+      "#Calculation\n",
+      "ELalpha=EKbita-EKalpha;     #energy of L alpha X ray(keV)\n",
+      "E2=-E-EKalpha;    #binding energy of L electron(keV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy of L alpha X ray is\",ELalpha,\"keV\"\n",
+      "print \"binding energy of L electron is\",E2,\"keV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy of L alpha X ray is 3.155 keV\n",
+        "binding energy of L electron is 3.524 keV\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.13, Page number 141"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "Z=11;    #atomic number\n",
+      "R=1.097*10**7;    #value of R(per m)\n",
+      "\n",
+      "#Calculation\n",
+      "E=(3*h*c*R*(Z-1)**2)/4;     #energy of k aplha X-ray(keV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy of k aplha X-ray is\",round(E*10**16,2),\"*10**-16 keV\"\n",
+      "print \"answer given in the book is wrong\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy of k aplha X-ray is 1.64 *10**-16 keV\n",
+        "answer given in the book is wrong\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter7_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter7_2.ipynb
new file mode 100755
index 00000000..45ed5766
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter7_2.ipynb
@@ -0,0 +1,258 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:1e02050388cdd15ca19e058c38c307c0fd0b145ef71769674c045940ea70b08b"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "7: Atomic physics"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.1, Page number 113"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mewB=9.27*10**-24;\n",
+      "B=3;   #magnetic field(T)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "E=2*mewB*B/e;    #energy difference(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy difference is\",round(E*10**4,2),\"*10**-4 eV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy difference is 3.48 *10**-4 eV\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.3, Page number 118"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "l=2;\n",
+      "s=1/2;\n",
+      "j1=2+(1/2);\n",
+      "j2=2-(1/2);\n",
+      "\n",
+      "#Calculation\n",
+      "L=math.sqrt(l*(l+1));   #value of L(hbar)\n",
+      "S=math.sqrt(s*(s+1));   #value of S(hbar)\n",
+      "J1=math.sqrt(j1*(j1+1));   #value of J for D5/2 state(hbar)\n",
+      "J2=math.sqrt(j2*(j2+1));   #value of J for D3/2 state(hbar)\n",
+      "costheta1=((j1*(j1+1))-(l*(l+1))-(s*(s+1)))/(2*L*S);\n",
+      "theta1=math.acos(costheta1);    #angle between L and S for D5/2(radian)\n",
+      "theta1=theta1*180/math.pi;    #angle between L and S for D5/2(degrees)\n",
+      "costheta2=((j2*(j2+1))-(l*(l+1))-(s*(s+1)))/(2*L*S);\n",
+      "theta2=math.acos(costheta2);    #angle between L and S for D3/2(radian)\n",
+      "theta2=theta2*180/math.pi;    #angle between L and S for D3/2(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"value of L is\",round(L,3),\"hbar\"\n",
+      "print \"value of S is\",round(S,3),\"hbar\"\n",
+      "print \"value of J for D5/2 state is\",round(J1,3),\"hbar\"\n",
+      "print \"value of J for D3/2 state is\",round(J2,3),\"hbar\"\n",
+      "print \"angle between L and S for D5/2 is\",round(theta1,2),\"degrees\"\n",
+      "print \"angle between L and S for D3/2 is\",int(theta2),\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "value of L is 2.449 hbar\n",
+        "value of S is 0.866 hbar\n",
+        "value of J for D5/2 state is 2.958 hbar\n",
+        "value of J for D3/2 state is 1.936 hbar\n",
+        "angle between L and S for D5/2 is 61.87 degrees\n",
+        "angle between L and S for D3/2 is 135 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 4
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.10, Page number 136"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "S=1;\n",
+      "L=1;  \n",
+      "J=1;\n",
+      "\n",
+      "#Calculation\n",
+      "a=L*(L+1)-(L*(L+1));\n",
+      "g1=1+(a/(2*L*(L+1)));    #lande's g-factor for pure orbital angular momentum\n",
+      "b=(S*(S+1)+(S*(S+1)))/(2*S*(S+1));   #lande's g-factor for pure spin angular momentum\n",
+      "g2=1+b;      #lande's g-factor for pure spin angular momentum\n",
+      "c=J*(J+1)+(S*(S+1))-(L*(L+1));\n",
+      "g3=1+(c/(2*J*(J+1)));   #lande's g-factor for state 3P1\n",
+      "\n",
+      "#Result\n",
+      "print \"lande's g-factor for pure orbital angular momentum is\",g1\n",
+      "print \"ande's g-factor for pure spin angular momentum is\",g2\n",
+      "print \"lande's g-factor for state 3P1 is\",g3"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "lande's g-factor for pure orbital angular momentum is 1.0\n",
+        "ande's g-factor for pure spin angular momentum is 2.0\n",
+        "lande's g-factor for state 3P1 is 1.5\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.12, Page number 141"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "EKalpha=21.99;   #energy in silver(keV)\n",
+      "EKbita=25.145;   #energy in silver(keV)\n",
+      "E=-25.514;    #energy of n=1 state(keV)\n",
+      " \n",
+      "#Calculation\n",
+      "ELalpha=EKbita-EKalpha;     #energy of L alpha X ray(keV)\n",
+      "E2=-E-EKalpha;    #binding energy of L electron(keV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy of L alpha X ray is\",ELalpha,\"keV\"\n",
+      "print \"binding energy of L electron is\",E2,\"keV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy of L alpha X ray is 3.155 keV\n",
+        "binding energy of L electron is 3.524 keV\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.13, Page number 141"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "Z=11;    #atomic number\n",
+      "R=1.097*10**7;    #value of R(per m)\n",
+      "\n",
+      "#Calculation\n",
+      "E=(3*h*c*R*(Z-1)**2)/4;     #energy of k aplha X-ray(keV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy of k aplha X-ray is\",round(E*10**16,2),\"*10**-16 keV\"\n",
+      "print \"answer given in the book is wrong\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy of k aplha X-ray is 1.64 *10**-16 keV\n",
+        "answer given in the book is wrong\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter7_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter7_3.ipynb
new file mode 100755
index 00000000..45ed5766
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter7_3.ipynb
@@ -0,0 +1,258 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:1e02050388cdd15ca19e058c38c307c0fd0b145ef71769674c045940ea70b08b"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "7: Atomic physics"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.1, Page number 113"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "mewB=9.27*10**-24;\n",
+      "B=3;   #magnetic field(T)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "E=2*mewB*B/e;    #energy difference(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy difference is\",round(E*10**4,2),\"*10**-4 eV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy difference is 3.48 *10**-4 eV\n"
+       ]
+      }
+     ],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.3, Page number 118"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "l=2;\n",
+      "s=1/2;\n",
+      "j1=2+(1/2);\n",
+      "j2=2-(1/2);\n",
+      "\n",
+      "#Calculation\n",
+      "L=math.sqrt(l*(l+1));   #value of L(hbar)\n",
+      "S=math.sqrt(s*(s+1));   #value of S(hbar)\n",
+      "J1=math.sqrt(j1*(j1+1));   #value of J for D5/2 state(hbar)\n",
+      "J2=math.sqrt(j2*(j2+1));   #value of J for D3/2 state(hbar)\n",
+      "costheta1=((j1*(j1+1))-(l*(l+1))-(s*(s+1)))/(2*L*S);\n",
+      "theta1=math.acos(costheta1);    #angle between L and S for D5/2(radian)\n",
+      "theta1=theta1*180/math.pi;    #angle between L and S for D5/2(degrees)\n",
+      "costheta2=((j2*(j2+1))-(l*(l+1))-(s*(s+1)))/(2*L*S);\n",
+      "theta2=math.acos(costheta2);    #angle between L and S for D3/2(radian)\n",
+      "theta2=theta2*180/math.pi;    #angle between L and S for D3/2(degrees)\n",
+      "\n",
+      "#Result\n",
+      "print \"value of L is\",round(L,3),\"hbar\"\n",
+      "print \"value of S is\",round(S,3),\"hbar\"\n",
+      "print \"value of J for D5/2 state is\",round(J1,3),\"hbar\"\n",
+      "print \"value of J for D3/2 state is\",round(J2,3),\"hbar\"\n",
+      "print \"angle between L and S for D5/2 is\",round(theta1,2),\"degrees\"\n",
+      "print \"angle between L and S for D3/2 is\",int(theta2),\"degrees\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "value of L is 2.449 hbar\n",
+        "value of S is 0.866 hbar\n",
+        "value of J for D5/2 state is 2.958 hbar\n",
+        "value of J for D3/2 state is 1.936 hbar\n",
+        "angle between L and S for D5/2 is 61.87 degrees\n",
+        "angle between L and S for D3/2 is 135 degrees\n"
+       ]
+      }
+     ],
+     "prompt_number": 4
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.10, Page number 136"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "S=1;\n",
+      "L=1;  \n",
+      "J=1;\n",
+      "\n",
+      "#Calculation\n",
+      "a=L*(L+1)-(L*(L+1));\n",
+      "g1=1+(a/(2*L*(L+1)));    #lande's g-factor for pure orbital angular momentum\n",
+      "b=(S*(S+1)+(S*(S+1)))/(2*S*(S+1));   #lande's g-factor for pure spin angular momentum\n",
+      "g2=1+b;      #lande's g-factor for pure spin angular momentum\n",
+      "c=J*(J+1)+(S*(S+1))-(L*(L+1));\n",
+      "g3=1+(c/(2*J*(J+1)));   #lande's g-factor for state 3P1\n",
+      "\n",
+      "#Result\n",
+      "print \"lande's g-factor for pure orbital angular momentum is\",g1\n",
+      "print \"ande's g-factor for pure spin angular momentum is\",g2\n",
+      "print \"lande's g-factor for state 3P1 is\",g3"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "lande's g-factor for pure orbital angular momentum is 1.0\n",
+        "ande's g-factor for pure spin angular momentum is 2.0\n",
+        "lande's g-factor for state 3P1 is 1.5\n"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.12, Page number 141"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "EKalpha=21.99;   #energy in silver(keV)\n",
+      "EKbita=25.145;   #energy in silver(keV)\n",
+      "E=-25.514;    #energy of n=1 state(keV)\n",
+      " \n",
+      "#Calculation\n",
+      "ELalpha=EKbita-EKalpha;     #energy of L alpha X ray(keV)\n",
+      "E2=-E-EKalpha;    #binding energy of L electron(keV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy of L alpha X ray is\",ELalpha,\"keV\"\n",
+      "print \"binding energy of L electron is\",E2,\"keV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy of L alpha X ray is 3.155 keV\n",
+        "binding energy of L electron is 3.524 keV\n"
+       ]
+      }
+     ],
+     "prompt_number": 8
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 7.13, Page number 141"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "Z=11;    #atomic number\n",
+      "R=1.097*10**7;    #value of R(per m)\n",
+      "\n",
+      "#Calculation\n",
+      "E=(3*h*c*R*(Z-1)**2)/4;     #energy of k aplha X-ray(keV)\n",
+      "\n",
+      "#Result\n",
+      "print \"energy of k aplha X-ray is\",round(E*10**16,2),\"*10**-16 keV\"\n",
+      "print \"answer given in the book is wrong\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "energy of k aplha X-ray is 1.64 *10**-16 keV\n",
+        "answer given in the book is wrong\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter8.ipynb b/Modern_Physics_By_G.Aruldas/Chapter8.ipynb
new file mode 100755
index 00000000..014cb0d9
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter8.ipynb
@@ -0,0 +1,116 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:3bf1b2120b5dacb9d86b4fa6efbc4300ebec3d48ce95ec80e2e6a8f936088a09"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "8: Statistical physics"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 8.2, Page number 164"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "rho=10.5;    #density of silver(g/cc)\n",
+      "M=108;    #atomic weight(g/mole)\n",
+      "NA=6.02*10**23;   #avagadro number(atoms/mole)\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "NbyV=rho*NA/M;    #number density of conduction electrons(per cc)\n",
+      "NbyV=NbyV*10**6;   #number density of conduction electrons(per m**3)\n",
+      "EF=(h**2/(8*m))*(3*NbyV/math.pi)**(2/3);   #fermi energy(J)\n",
+      "EF=EF/e;   #fermi energy(eV)\n",
+      "E=3*EF/5;    #mean energy of electron(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"number density of conduction electrons is\",round(NbyV/10**28,2),\"*10**28 per m**3\"\n",
+      "print \"fermi energy is\",round(EF,2),\"eV\"\n",
+      "print \"mean energy of electron is\",round(E,2),\"eV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "number density of conduction electrons is 5.85 *10**28 per m**3\n",
+        "fermi energy is 5.51 eV\n",
+        "mean energy of electron is 3.31 eV\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 8.3, Page number 164"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "T=300;    #temperature(K)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "EF=5.49;    #fermi energy(eV)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "R=1;   #assume\n",
+      "\n",
+      "#Calculation\n",
+      "CV=math.pi**2*k*T*R/(2*EF*e);    #electronic contribution of Silver(R)\n",
+      "\n",
+      "#Result\n",
+      "print \"electronic contribution of Silver is\",round(CV,5),\"R\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "electronic contribution of Silver is 0.02326 R\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter8_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter8_1.ipynb
new file mode 100755
index 00000000..014cb0d9
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter8_1.ipynb
@@ -0,0 +1,116 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:3bf1b2120b5dacb9d86b4fa6efbc4300ebec3d48ce95ec80e2e6a8f936088a09"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "8: Statistical physics"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 8.2, Page number 164"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "rho=10.5;    #density of silver(g/cc)\n",
+      "M=108;    #atomic weight(g/mole)\n",
+      "NA=6.02*10**23;   #avagadro number(atoms/mole)\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "NbyV=rho*NA/M;    #number density of conduction electrons(per cc)\n",
+      "NbyV=NbyV*10**6;   #number density of conduction electrons(per m**3)\n",
+      "EF=(h**2/(8*m))*(3*NbyV/math.pi)**(2/3);   #fermi energy(J)\n",
+      "EF=EF/e;   #fermi energy(eV)\n",
+      "E=3*EF/5;    #mean energy of electron(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"number density of conduction electrons is\",round(NbyV/10**28,2),\"*10**28 per m**3\"\n",
+      "print \"fermi energy is\",round(EF,2),\"eV\"\n",
+      "print \"mean energy of electron is\",round(E,2),\"eV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "number density of conduction electrons is 5.85 *10**28 per m**3\n",
+        "fermi energy is 5.51 eV\n",
+        "mean energy of electron is 3.31 eV\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 8.3, Page number 164"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "T=300;    #temperature(K)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "EF=5.49;    #fermi energy(eV)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "R=1;   #assume\n",
+      "\n",
+      "#Calculation\n",
+      "CV=math.pi**2*k*T*R/(2*EF*e);    #electronic contribution of Silver(R)\n",
+      "\n",
+      "#Result\n",
+      "print \"electronic contribution of Silver is\",round(CV,5),\"R\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "electronic contribution of Silver is 0.02326 R\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter8_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter8_2.ipynb
new file mode 100755
index 00000000..014cb0d9
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter8_2.ipynb
@@ -0,0 +1,116 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:3bf1b2120b5dacb9d86b4fa6efbc4300ebec3d48ce95ec80e2e6a8f936088a09"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "8: Statistical physics"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 8.2, Page number 164"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "rho=10.5;    #density of silver(g/cc)\n",
+      "M=108;    #atomic weight(g/mole)\n",
+      "NA=6.02*10**23;   #avagadro number(atoms/mole)\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "NbyV=rho*NA/M;    #number density of conduction electrons(per cc)\n",
+      "NbyV=NbyV*10**6;   #number density of conduction electrons(per m**3)\n",
+      "EF=(h**2/(8*m))*(3*NbyV/math.pi)**(2/3);   #fermi energy(J)\n",
+      "EF=EF/e;   #fermi energy(eV)\n",
+      "E=3*EF/5;    #mean energy of electron(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"number density of conduction electrons is\",round(NbyV/10**28,2),\"*10**28 per m**3\"\n",
+      "print \"fermi energy is\",round(EF,2),\"eV\"\n",
+      "print \"mean energy of electron is\",round(E,2),\"eV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "number density of conduction electrons is 5.85 *10**28 per m**3\n",
+        "fermi energy is 5.51 eV\n",
+        "mean energy of electron is 3.31 eV\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 8.3, Page number 164"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "T=300;    #temperature(K)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "EF=5.49;    #fermi energy(eV)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "R=1;   #assume\n",
+      "\n",
+      "#Calculation\n",
+      "CV=math.pi**2*k*T*R/(2*EF*e);    #electronic contribution of Silver(R)\n",
+      "\n",
+      "#Result\n",
+      "print \"electronic contribution of Silver is\",round(CV,5),\"R\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "electronic contribution of Silver is 0.02326 R\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter8_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter8_3.ipynb
new file mode 100755
index 00000000..014cb0d9
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter8_3.ipynb
@@ -0,0 +1,116 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:3bf1b2120b5dacb9d86b4fa6efbc4300ebec3d48ce95ec80e2e6a8f936088a09"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "8: Statistical physics"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 8.2, Page number 164"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "rho=10.5;    #density of silver(g/cc)\n",
+      "M=108;    #atomic weight(g/mole)\n",
+      "NA=6.02*10**23;   #avagadro number(atoms/mole)\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "m=9.1*10**-31;    #mass of electron(kg)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "\n",
+      "#Calculation\n",
+      "NbyV=rho*NA/M;    #number density of conduction electrons(per cc)\n",
+      "NbyV=NbyV*10**6;   #number density of conduction electrons(per m**3)\n",
+      "EF=(h**2/(8*m))*(3*NbyV/math.pi)**(2/3);   #fermi energy(J)\n",
+      "EF=EF/e;   #fermi energy(eV)\n",
+      "E=3*EF/5;    #mean energy of electron(eV)\n",
+      "\n",
+      "#Result\n",
+      "print \"number density of conduction electrons is\",round(NbyV/10**28,2),\"*10**28 per m**3\"\n",
+      "print \"fermi energy is\",round(EF,2),\"eV\"\n",
+      "print \"mean energy of electron is\",round(E,2),\"eV\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "number density of conduction electrons is 5.85 *10**28 per m**3\n",
+        "fermi energy is 5.51 eV\n",
+        "mean energy of electron is 3.31 eV\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 8.3, Page number 164"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "T=300;    #temperature(K)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "EF=5.49;    #fermi energy(eV)\n",
+      "e=1.6*10**-19;   #conversion factor from J to eV\n",
+      "R=1;   #assume\n",
+      "\n",
+      "#Calculation\n",
+      "CV=math.pi**2*k*T*R/(2*EF*e);    #electronic contribution of Silver(R)\n",
+      "\n",
+      "#Result\n",
+      "print \"electronic contribution of Silver is\",round(CV,5),\"R\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "electronic contribution of Silver is 0.02326 R\n"
+       ]
+      }
+     ],
+     "prompt_number": 9
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter9.ipynb b/Modern_Physics_By_G.Aruldas/Chapter9.ipynb
new file mode 100755
index 00000000..fa1ac5e9
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter9.ipynb
@@ -0,0 +1,418 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:d1e925900cff60559a1ba3f62c2c267140215c90675c4dba42b1a473becca175"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "9: Molecular spectra"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.1, Page number 172"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "twoB=3.8626;   #average spacing(per cm)\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #speed of light(m/s)\n",
+      "NA=6.022*10**23;   #avagadro number(atoms/mole)\n",
+      "mC=0.012;   #isotopic mass of C(kg/mol)\n",
+      "mO=0.016;   #isotopic mass of O(kg/mol)\n",
+      "\n",
+      "#Calculation\n",
+      "B=(twoB/2)*100;   #average spacing(per m)\n",
+      "I=h/(8*math.pi**2*B*c); \n",
+      "mew=mC*mO/((mC+mO)*NA);   #reduced mass(kg)\n",
+      "r=math.sqrt(I/mew);   #bond length(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"bond length is\",round(r*10**10,3),\"*10**-10 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "bond length is 1.128 *10**-10 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.2, Page number 173"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "T=300;    #temperature(K)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #speed of light(m/s)\n",
+      "lamda=10**-2;    #wavelength(m)\n",
+      "\n",
+      "#Calculation\n",
+      "E=3*k*T/2;    #kinetic energy(J)\n",
+      "deltaE=h*c/lamda;   #energy seperation(J)\n",
+      "\n",
+      "#Result\n",
+      "print \"kinetic energy is\",E,\"J\"\n",
+      "print \"energy seperation is\",round(deltaE*10**23),\"*10**-23 J\"\n",
+      "print \"deltaE is much smaller than E. hence substantial number of molecules will be there\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "kinetic energy is 6.21e-21 J\n",
+        "energy seperation is 2.0 *10**-23 J\n",
+        "deltaE is much smaller than E. hence substantial number of molecules will be there\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.3, Page number 175"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "ff=1876.06;    #frequency of fundamental(per cm)\n",
+      "fo=3724.2;     #frequency of 1st overtone(per cm)\n",
+      "\n",
+      "#Calculation\n",
+      "#ff=vebar*(1-(2*xe)) and fo=2*vebar*(1-(3*xe)). on solcing we get\n",
+      "vebar=1903.98;   #equilibrium vibration frequency(per cm)\n",
+      "xe=7.33*10**-3;   #anharmonicity constant\n",
+      "E=vebar/2;   #zero point energy(per cm)\n",
+      "\n",
+      "#Result\n",
+      "print \"equilibrium vibration frequency is\",vebar,\"per cm\"\n",
+      "print \"anharmonicity constant is\",round(xe*10**3,2),\"*10**-3\"\n",
+      "print \"zero point energy is\",round(E),\"per cm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "equilibrium vibration frequency is 1903.98 per cm\n",
+        "anharmonicity constant is 7.33 *10**-3\n",
+        "zero point energy is 952.0 per cm\n"
+       ]
+      }
+     ],
+     "prompt_number": 10
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.4, Page number 175"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m=1.67*10**-27;    #mass of proton(kg)\n",
+      "m1=1.0087;    #mass of 1H(u)\n",
+      "m2=35.453;    #mass of Cl(u)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda0=3.465*10**-6;   #wavelength(m)\n",
+      "\n",
+      "#Calculation\n",
+      "mew=m*m1*m2/(m1+m2);     #reduced mass(kg)\n",
+      "k=4*math.pi**2*mew*(c/lamda0)**2;   #force constant(N/m)\n",
+      "\n",
+      "#Result\n",
+      "print \"force constant is\",round(k,1),\"N/m\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "force constant is 484.7 N/m\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.5, Page number 187"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "lamdae=4358.3*10**-8;      #excited wavelength(cm)\n",
+      "lamda=4768.5*10**-8;    #wavelength(cm)\n",
+      "\n",
+      "#Calculation\n",
+      "wne=1/lamdae;    #wave number of exciting radiation(per cm)\n",
+      "wn=1/lamda;   #wave number of Raman line(per cm)\n",
+      "new=wne-wn;   #vibrational frequency(per cm)\n",
+      "\n",
+      "#Result\n",
+      "print \"vibrational frequency is\",round(new),\"per cm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "vibrational frequency is 1974.0 per cm\n"
+       ]
+      }
+     ],
+     "prompt_number": 15
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.6, Page number 188"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #speed of light(m/s)\n",
+      "sixB=346;   #1st rotational Raman line(per cm)\n",
+      "m1=1.673*10**-27;    #mass of proton(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "m2=m1;\n",
+      "B=(sixB/6)*100;   #average spacing(per m)\n",
+      "I=h/(8*math.pi**2*B*c); \n",
+      "mew=m1*m2/(m1+m2);   #reduced mass(kg)\n",
+      "r=math.sqrt(I/mew);   #bond length(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"bond length is\",round(r*10**10,3),\"*10**-10 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "bond length is 0.762 *10**-10 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 18
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.7, Page number 193"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "gN=5.585;    #value of gN\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "new=120*10**6;   #frequency(Hz)\n",
+      "mewn=5.0508*10**-27;\n",
+      "\n",
+      "#Calculation\n",
+      "B0=h*new/(gN*mewn);    #magnetic field strength(T)\n",
+      "\n",
+      "#Result\n",
+      "print \"magnetic field strength is\",round(B0,3),\"T\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "magnetic field strength is 2.819 T\n"
+       ]
+      }
+     ],
+     "prompt_number": 20
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.8, Page number 194"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "gN=5.585;    #value of gN\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "mewn=5.0508*10**-27;\n",
+      "B0=1.65;    #magnetic field(T)\n",
+      "new=510*10**6;   #frequency separation(Hz)\n",
+      "\n",
+      "#Calculation\n",
+      "new0=gN*mewn*B0/h;\n",
+      "delta=new/new0;    #chemical shift(ppm)\n",
+      "\n",
+      "#Result\n",
+      "print \"chemical shift is\",round(delta,2),\"ppm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "chemical shift is 7.26 ppm\n"
+       ]
+      }
+     ],
+     "prompt_number": 24
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.10, Page number 198"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "new=35*10**9;    #frequency(Hz)\n",
+      "mewB=9.27*10**-24;\n",
+      "B0=1.3;    #magnetic field(T)\n",
+      "\n",
+      "#Calculation\n",
+      "g=h*new/(mewB*B0);   #electron g-factor\n",
+      "\n",
+      "#Result\n",
+      "print \"electron g-factor is\",round(g,3)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "electron g-factor is 1.924\n"
+       ]
+      }
+     ],
+     "prompt_number": 26
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter9_1.ipynb b/Modern_Physics_By_G.Aruldas/Chapter9_1.ipynb
new file mode 100755
index 00000000..fa1ac5e9
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter9_1.ipynb
@@ -0,0 +1,418 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:d1e925900cff60559a1ba3f62c2c267140215c90675c4dba42b1a473becca175"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "9: Molecular spectra"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.1, Page number 172"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "twoB=3.8626;   #average spacing(per cm)\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #speed of light(m/s)\n",
+      "NA=6.022*10**23;   #avagadro number(atoms/mole)\n",
+      "mC=0.012;   #isotopic mass of C(kg/mol)\n",
+      "mO=0.016;   #isotopic mass of O(kg/mol)\n",
+      "\n",
+      "#Calculation\n",
+      "B=(twoB/2)*100;   #average spacing(per m)\n",
+      "I=h/(8*math.pi**2*B*c); \n",
+      "mew=mC*mO/((mC+mO)*NA);   #reduced mass(kg)\n",
+      "r=math.sqrt(I/mew);   #bond length(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"bond length is\",round(r*10**10,3),\"*10**-10 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "bond length is 1.128 *10**-10 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.2, Page number 173"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "T=300;    #temperature(K)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #speed of light(m/s)\n",
+      "lamda=10**-2;    #wavelength(m)\n",
+      "\n",
+      "#Calculation\n",
+      "E=3*k*T/2;    #kinetic energy(J)\n",
+      "deltaE=h*c/lamda;   #energy seperation(J)\n",
+      "\n",
+      "#Result\n",
+      "print \"kinetic energy is\",E,\"J\"\n",
+      "print \"energy seperation is\",round(deltaE*10**23),\"*10**-23 J\"\n",
+      "print \"deltaE is much smaller than E. hence substantial number of molecules will be there\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "kinetic energy is 6.21e-21 J\n",
+        "energy seperation is 2.0 *10**-23 J\n",
+        "deltaE is much smaller than E. hence substantial number of molecules will be there\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.3, Page number 175"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "ff=1876.06;    #frequency of fundamental(per cm)\n",
+      "fo=3724.2;     #frequency of 1st overtone(per cm)\n",
+      "\n",
+      "#Calculation\n",
+      "#ff=vebar*(1-(2*xe)) and fo=2*vebar*(1-(3*xe)). on solcing we get\n",
+      "vebar=1903.98;   #equilibrium vibration frequency(per cm)\n",
+      "xe=7.33*10**-3;   #anharmonicity constant\n",
+      "E=vebar/2;   #zero point energy(per cm)\n",
+      "\n",
+      "#Result\n",
+      "print \"equilibrium vibration frequency is\",vebar,\"per cm\"\n",
+      "print \"anharmonicity constant is\",round(xe*10**3,2),\"*10**-3\"\n",
+      "print \"zero point energy is\",round(E),\"per cm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "equilibrium vibration frequency is 1903.98 per cm\n",
+        "anharmonicity constant is 7.33 *10**-3\n",
+        "zero point energy is 952.0 per cm\n"
+       ]
+      }
+     ],
+     "prompt_number": 10
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.4, Page number 175"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m=1.67*10**-27;    #mass of proton(kg)\n",
+      "m1=1.0087;    #mass of 1H(u)\n",
+      "m2=35.453;    #mass of Cl(u)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda0=3.465*10**-6;   #wavelength(m)\n",
+      "\n",
+      "#Calculation\n",
+      "mew=m*m1*m2/(m1+m2);     #reduced mass(kg)\n",
+      "k=4*math.pi**2*mew*(c/lamda0)**2;   #force constant(N/m)\n",
+      "\n",
+      "#Result\n",
+      "print \"force constant is\",round(k,1),\"N/m\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "force constant is 484.7 N/m\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.5, Page number 187"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "lamdae=4358.3*10**-8;      #excited wavelength(cm)\n",
+      "lamda=4768.5*10**-8;    #wavelength(cm)\n",
+      "\n",
+      "#Calculation\n",
+      "wne=1/lamdae;    #wave number of exciting radiation(per cm)\n",
+      "wn=1/lamda;   #wave number of Raman line(per cm)\n",
+      "new=wne-wn;   #vibrational frequency(per cm)\n",
+      "\n",
+      "#Result\n",
+      "print \"vibrational frequency is\",round(new),\"per cm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "vibrational frequency is 1974.0 per cm\n"
+       ]
+      }
+     ],
+     "prompt_number": 15
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.6, Page number 188"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #speed of light(m/s)\n",
+      "sixB=346;   #1st rotational Raman line(per cm)\n",
+      "m1=1.673*10**-27;    #mass of proton(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "m2=m1;\n",
+      "B=(sixB/6)*100;   #average spacing(per m)\n",
+      "I=h/(8*math.pi**2*B*c); \n",
+      "mew=m1*m2/(m1+m2);   #reduced mass(kg)\n",
+      "r=math.sqrt(I/mew);   #bond length(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"bond length is\",round(r*10**10,3),\"*10**-10 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "bond length is 0.762 *10**-10 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 18
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.7, Page number 193"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "gN=5.585;    #value of gN\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "new=120*10**6;   #frequency(Hz)\n",
+      "mewn=5.0508*10**-27;\n",
+      "\n",
+      "#Calculation\n",
+      "B0=h*new/(gN*mewn);    #magnetic field strength(T)\n",
+      "\n",
+      "#Result\n",
+      "print \"magnetic field strength is\",round(B0,3),\"T\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "magnetic field strength is 2.819 T\n"
+       ]
+      }
+     ],
+     "prompt_number": 20
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.8, Page number 194"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "gN=5.585;    #value of gN\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "mewn=5.0508*10**-27;\n",
+      "B0=1.65;    #magnetic field(T)\n",
+      "new=510*10**6;   #frequency separation(Hz)\n",
+      "\n",
+      "#Calculation\n",
+      "new0=gN*mewn*B0/h;\n",
+      "delta=new/new0;    #chemical shift(ppm)\n",
+      "\n",
+      "#Result\n",
+      "print \"chemical shift is\",round(delta,2),\"ppm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "chemical shift is 7.26 ppm\n"
+       ]
+      }
+     ],
+     "prompt_number": 24
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.10, Page number 198"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "new=35*10**9;    #frequency(Hz)\n",
+      "mewB=9.27*10**-24;\n",
+      "B0=1.3;    #magnetic field(T)\n",
+      "\n",
+      "#Calculation\n",
+      "g=h*new/(mewB*B0);   #electron g-factor\n",
+      "\n",
+      "#Result\n",
+      "print \"electron g-factor is\",round(g,3)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "electron g-factor is 1.924\n"
+       ]
+      }
+     ],
+     "prompt_number": 26
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter9_2.ipynb b/Modern_Physics_By_G.Aruldas/Chapter9_2.ipynb
new file mode 100755
index 00000000..fa1ac5e9
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter9_2.ipynb
@@ -0,0 +1,418 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:d1e925900cff60559a1ba3f62c2c267140215c90675c4dba42b1a473becca175"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "9: Molecular spectra"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.1, Page number 172"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "twoB=3.8626;   #average spacing(per cm)\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #speed of light(m/s)\n",
+      "NA=6.022*10**23;   #avagadro number(atoms/mole)\n",
+      "mC=0.012;   #isotopic mass of C(kg/mol)\n",
+      "mO=0.016;   #isotopic mass of O(kg/mol)\n",
+      "\n",
+      "#Calculation\n",
+      "B=(twoB/2)*100;   #average spacing(per m)\n",
+      "I=h/(8*math.pi**2*B*c); \n",
+      "mew=mC*mO/((mC+mO)*NA);   #reduced mass(kg)\n",
+      "r=math.sqrt(I/mew);   #bond length(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"bond length is\",round(r*10**10,3),\"*10**-10 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "bond length is 1.128 *10**-10 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.2, Page number 173"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "T=300;    #temperature(K)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #speed of light(m/s)\n",
+      "lamda=10**-2;    #wavelength(m)\n",
+      "\n",
+      "#Calculation\n",
+      "E=3*k*T/2;    #kinetic energy(J)\n",
+      "deltaE=h*c/lamda;   #energy seperation(J)\n",
+      "\n",
+      "#Result\n",
+      "print \"kinetic energy is\",E,\"J\"\n",
+      "print \"energy seperation is\",round(deltaE*10**23),\"*10**-23 J\"\n",
+      "print \"deltaE is much smaller than E. hence substantial number of molecules will be there\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "kinetic energy is 6.21e-21 J\n",
+        "energy seperation is 2.0 *10**-23 J\n",
+        "deltaE is much smaller than E. hence substantial number of molecules will be there\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.3, Page number 175"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "ff=1876.06;    #frequency of fundamental(per cm)\n",
+      "fo=3724.2;     #frequency of 1st overtone(per cm)\n",
+      "\n",
+      "#Calculation\n",
+      "#ff=vebar*(1-(2*xe)) and fo=2*vebar*(1-(3*xe)). on solcing we get\n",
+      "vebar=1903.98;   #equilibrium vibration frequency(per cm)\n",
+      "xe=7.33*10**-3;   #anharmonicity constant\n",
+      "E=vebar/2;   #zero point energy(per cm)\n",
+      "\n",
+      "#Result\n",
+      "print \"equilibrium vibration frequency is\",vebar,\"per cm\"\n",
+      "print \"anharmonicity constant is\",round(xe*10**3,2),\"*10**-3\"\n",
+      "print \"zero point energy is\",round(E),\"per cm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "equilibrium vibration frequency is 1903.98 per cm\n",
+        "anharmonicity constant is 7.33 *10**-3\n",
+        "zero point energy is 952.0 per cm\n"
+       ]
+      }
+     ],
+     "prompt_number": 10
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.4, Page number 175"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m=1.67*10**-27;    #mass of proton(kg)\n",
+      "m1=1.0087;    #mass of 1H(u)\n",
+      "m2=35.453;    #mass of Cl(u)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda0=3.465*10**-6;   #wavelength(m)\n",
+      "\n",
+      "#Calculation\n",
+      "mew=m*m1*m2/(m1+m2);     #reduced mass(kg)\n",
+      "k=4*math.pi**2*mew*(c/lamda0)**2;   #force constant(N/m)\n",
+      "\n",
+      "#Result\n",
+      "print \"force constant is\",round(k,1),\"N/m\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "force constant is 484.7 N/m\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.5, Page number 187"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "lamdae=4358.3*10**-8;      #excited wavelength(cm)\n",
+      "lamda=4768.5*10**-8;    #wavelength(cm)\n",
+      "\n",
+      "#Calculation\n",
+      "wne=1/lamdae;    #wave number of exciting radiation(per cm)\n",
+      "wn=1/lamda;   #wave number of Raman line(per cm)\n",
+      "new=wne-wn;   #vibrational frequency(per cm)\n",
+      "\n",
+      "#Result\n",
+      "print \"vibrational frequency is\",round(new),\"per cm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "vibrational frequency is 1974.0 per cm\n"
+       ]
+      }
+     ],
+     "prompt_number": 15
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.6, Page number 188"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #speed of light(m/s)\n",
+      "sixB=346;   #1st rotational Raman line(per cm)\n",
+      "m1=1.673*10**-27;    #mass of proton(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "m2=m1;\n",
+      "B=(sixB/6)*100;   #average spacing(per m)\n",
+      "I=h/(8*math.pi**2*B*c); \n",
+      "mew=m1*m2/(m1+m2);   #reduced mass(kg)\n",
+      "r=math.sqrt(I/mew);   #bond length(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"bond length is\",round(r*10**10,3),\"*10**-10 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "bond length is 0.762 *10**-10 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 18
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.7, Page number 193"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "gN=5.585;    #value of gN\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "new=120*10**6;   #frequency(Hz)\n",
+      "mewn=5.0508*10**-27;\n",
+      "\n",
+      "#Calculation\n",
+      "B0=h*new/(gN*mewn);    #magnetic field strength(T)\n",
+      "\n",
+      "#Result\n",
+      "print \"magnetic field strength is\",round(B0,3),\"T\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "magnetic field strength is 2.819 T\n"
+       ]
+      }
+     ],
+     "prompt_number": 20
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.8, Page number 194"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "gN=5.585;    #value of gN\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "mewn=5.0508*10**-27;\n",
+      "B0=1.65;    #magnetic field(T)\n",
+      "new=510*10**6;   #frequency separation(Hz)\n",
+      "\n",
+      "#Calculation\n",
+      "new0=gN*mewn*B0/h;\n",
+      "delta=new/new0;    #chemical shift(ppm)\n",
+      "\n",
+      "#Result\n",
+      "print \"chemical shift is\",round(delta,2),\"ppm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "chemical shift is 7.26 ppm\n"
+       ]
+      }
+     ],
+     "prompt_number": 24
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.10, Page number 198"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "new=35*10**9;    #frequency(Hz)\n",
+      "mewB=9.27*10**-24;\n",
+      "B0=1.3;    #magnetic field(T)\n",
+      "\n",
+      "#Calculation\n",
+      "g=h*new/(mewB*B0);   #electron g-factor\n",
+      "\n",
+      "#Result\n",
+      "print \"electron g-factor is\",round(g,3)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "electron g-factor is 1.924\n"
+       ]
+      }
+     ],
+     "prompt_number": 26
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
diff --git a/Modern_Physics_By_G.Aruldas/Chapter9_3.ipynb b/Modern_Physics_By_G.Aruldas/Chapter9_3.ipynb
new file mode 100755
index 00000000..fa1ac5e9
--- /dev/null
+++ b/Modern_Physics_By_G.Aruldas/Chapter9_3.ipynb
@@ -0,0 +1,418 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:d1e925900cff60559a1ba3f62c2c267140215c90675c4dba42b1a473becca175"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "9: Molecular spectra"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.1, Page number 172"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "twoB=3.8626;   #average spacing(per cm)\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #speed of light(m/s)\n",
+      "NA=6.022*10**23;   #avagadro number(atoms/mole)\n",
+      "mC=0.012;   #isotopic mass of C(kg/mol)\n",
+      "mO=0.016;   #isotopic mass of O(kg/mol)\n",
+      "\n",
+      "#Calculation\n",
+      "B=(twoB/2)*100;   #average spacing(per m)\n",
+      "I=h/(8*math.pi**2*B*c); \n",
+      "mew=mC*mO/((mC+mO)*NA);   #reduced mass(kg)\n",
+      "r=math.sqrt(I/mew);   #bond length(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"bond length is\",round(r*10**10,3),\"*10**-10 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "bond length is 1.128 *10**-10 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.2, Page number 173"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "T=300;    #temperature(K)\n",
+      "k=1.38*10**-23;   #boltzmann constant(J/K)\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #speed of light(m/s)\n",
+      "lamda=10**-2;    #wavelength(m)\n",
+      "\n",
+      "#Calculation\n",
+      "E=3*k*T/2;    #kinetic energy(J)\n",
+      "deltaE=h*c/lamda;   #energy seperation(J)\n",
+      "\n",
+      "#Result\n",
+      "print \"kinetic energy is\",E,\"J\"\n",
+      "print \"energy seperation is\",round(deltaE*10**23),\"*10**-23 J\"\n",
+      "print \"deltaE is much smaller than E. hence substantial number of molecules will be there\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "kinetic energy is 6.21e-21 J\n",
+        "energy seperation is 2.0 *10**-23 J\n",
+        "deltaE is much smaller than E. hence substantial number of molecules will be there\n"
+       ]
+      }
+     ],
+     "prompt_number": 5
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.3, Page number 175"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "ff=1876.06;    #frequency of fundamental(per cm)\n",
+      "fo=3724.2;     #frequency of 1st overtone(per cm)\n",
+      "\n",
+      "#Calculation\n",
+      "#ff=vebar*(1-(2*xe)) and fo=2*vebar*(1-(3*xe)). on solcing we get\n",
+      "vebar=1903.98;   #equilibrium vibration frequency(per cm)\n",
+      "xe=7.33*10**-3;   #anharmonicity constant\n",
+      "E=vebar/2;   #zero point energy(per cm)\n",
+      "\n",
+      "#Result\n",
+      "print \"equilibrium vibration frequency is\",vebar,\"per cm\"\n",
+      "print \"anharmonicity constant is\",round(xe*10**3,2),\"*10**-3\"\n",
+      "print \"zero point energy is\",round(E),\"per cm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "equilibrium vibration frequency is 1903.98 per cm\n",
+        "anharmonicity constant is 7.33 *10**-3\n",
+        "zero point energy is 952.0 per cm\n"
+       ]
+      }
+     ],
+     "prompt_number": 10
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.4, Page number 175"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "m=1.67*10**-27;    #mass of proton(kg)\n",
+      "m1=1.0087;    #mass of 1H(u)\n",
+      "m2=35.453;    #mass of Cl(u)\n",
+      "c=3*10**8;    #velocity of light(m/sec)\n",
+      "lamda0=3.465*10**-6;   #wavelength(m)\n",
+      "\n",
+      "#Calculation\n",
+      "mew=m*m1*m2/(m1+m2);     #reduced mass(kg)\n",
+      "k=4*math.pi**2*mew*(c/lamda0)**2;   #force constant(N/m)\n",
+      "\n",
+      "#Result\n",
+      "print \"force constant is\",round(k,1),\"N/m\"\n",
+      "print \"answer varies due to rounding off errors\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "force constant is 484.7 N/m\n",
+        "answer varies due to rounding off errors\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.5, Page number 187"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "lamdae=4358.3*10**-8;      #excited wavelength(cm)\n",
+      "lamda=4768.5*10**-8;    #wavelength(cm)\n",
+      "\n",
+      "#Calculation\n",
+      "wne=1/lamdae;    #wave number of exciting radiation(per cm)\n",
+      "wn=1/lamda;   #wave number of Raman line(per cm)\n",
+      "new=wne-wn;   #vibrational frequency(per cm)\n",
+      "\n",
+      "#Result\n",
+      "print \"vibrational frequency is\",round(new),\"per cm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "vibrational frequency is 1974.0 per cm\n"
+       ]
+      }
+     ],
+     "prompt_number": 15
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.6, Page number 188"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "c=3*10**8;    #speed of light(m/s)\n",
+      "sixB=346;   #1st rotational Raman line(per cm)\n",
+      "m1=1.673*10**-27;    #mass of proton(kg)\n",
+      "\n",
+      "#Calculation\n",
+      "m2=m1;\n",
+      "B=(sixB/6)*100;   #average spacing(per m)\n",
+      "I=h/(8*math.pi**2*B*c); \n",
+      "mew=m1*m2/(m1+m2);   #reduced mass(kg)\n",
+      "r=math.sqrt(I/mew);   #bond length(m)\n",
+      "\n",
+      "#Result\n",
+      "print \"bond length is\",round(r*10**10,3),\"*10**-10 m\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "bond length is 0.762 *10**-10 m\n"
+       ]
+      }
+     ],
+     "prompt_number": 18
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.7, Page number 193"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "gN=5.585;    #value of gN\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "new=120*10**6;   #frequency(Hz)\n",
+      "mewn=5.0508*10**-27;\n",
+      "\n",
+      "#Calculation\n",
+      "B0=h*new/(gN*mewn);    #magnetic field strength(T)\n",
+      "\n",
+      "#Result\n",
+      "print \"magnetic field strength is\",round(B0,3),\"T\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "magnetic field strength is 2.819 T\n"
+       ]
+      }
+     ],
+     "prompt_number": 20
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.8, Page number 194"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "gN=5.585;    #value of gN\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "mewn=5.0508*10**-27;\n",
+      "B0=1.65;    #magnetic field(T)\n",
+      "new=510*10**6;   #frequency separation(Hz)\n",
+      "\n",
+      "#Calculation\n",
+      "new0=gN*mewn*B0/h;\n",
+      "delta=new/new0;    #chemical shift(ppm)\n",
+      "\n",
+      "#Result\n",
+      "print \"chemical shift is\",round(delta,2),\"ppm\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "chemical shift is 7.26 ppm\n"
+       ]
+      }
+     ],
+     "prompt_number": 24
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example number 9.10, Page number 198"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "#importing modules\n",
+      "import math\n",
+      "from __future__ import division\n",
+      "\n",
+      "#Variable declaration\n",
+      "h=6.626*10**-34;    #planck's constant(Js)\n",
+      "new=35*10**9;    #frequency(Hz)\n",
+      "mewB=9.27*10**-24;\n",
+      "B0=1.3;    #magnetic field(T)\n",
+      "\n",
+      "#Calculation\n",
+      "g=h*new/(mewB*B0);   #electron g-factor\n",
+      "\n",
+      "#Result\n",
+      "print \"electron g-factor is\",round(g,3)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "electron g-factor is 1.924\n"
+       ]
+      }
+     ],
+     "prompt_number": 26
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file
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