{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#11: Lasers"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example number 11.1, Page number 11.55"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "intensity of laser beam is 1.5 *10**4 watt/m**2\n",
      "answer given in the book is wrong\n"
     ]
    }
   ],
   "source": [
    "#importing modules\n",
    "import math\n",
    "from __future__ import division\n",
    "\n",
    "#Variable declaration\n",
    "P=20*10**-3;      #power(watt)\n",
    "r=1.3/2;     #radius(mm)\n",
    "\n",
    "#Calculation\n",
    "r=r*10**-3;    #radius(m)\n",
    "I=P/(math.pi*r**2);     #intensity of laser beam(watt/m**2)\n",
    "\n",
    "#Result\n",
    "print \"intensity of laser beam is\",round(I/10**4,1),\"*10**4 watt/m**2\"\n",
    "print \"answer given in the book is wrong\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example number 11.2, Page number 11.56"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "mode seperation in frequency is 2.5 *10**8 Hz\n"
     ]
    }
   ],
   "source": [
    "#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",
    "L=0.6;      #distance(m)\n",
    "\n",
    "#Calculation\n",
    "delta_v=c/(2*L);    #mode seperation in frequency(Hz)\n",
    "\n",
    "#Result\n",
    "print \"mode seperation in frequency is\",delta_v/10**8,\"*10**8 Hz\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example number 11.3, Page number 11.56"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "coherence length is 1.5 *10**-2 m\n",
      "band width is 2.0 *10**10 Hz\n",
      "line width is 0.026 nm\n"
     ]
    }
   ],
   "source": [
    "#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",
    "delta_t=0.05*10**-9;    #time(s)\n",
    "lamda=623.8*10**-9;    #wavelength(m)\n",
    "\n",
    "#Calculation\n",
    "cl=c*delta_t;    #coherence length(m)\n",
    "delta_v=1/delta_t;    #band width(Hz)\n",
    "delta_lamda=lamda**2*delta_v/c;    #line width(m)\n",
    "\n",
    "#Result\n",
    "print \"coherence length is\",cl*10**2,\"*10**-2 m\"\n",
    "print \"band width is\",delta_v/10**10,\"*10**10 Hz\"\n",
    "print \"line width is\",round(delta_lamda*10**9,3),\"nm\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example number 11.4, Page number 11.56"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "energy difference is 1.96 eV\n"
     ]
    }
   ],
   "source": [
    "#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",
    "h=6.63*10**-34;    #plank's constant(Js)\n",
    "lamda=632.8*10**-9;    #wavelength(m)\n",
    "e=1.6*10**-19;     #charge(coulomb)\n",
    "\n",
    "#Calculation\n",
    "E=c*h/(lamda*e);    #energy difference(eV)\n",
    "\n",
    "#Result\n",
    "print \"energy difference is\",round(E,2),\"eV\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example number 11.5, Page number 11.57"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "ratio of population is 8.95 *10**-32\n",
      "answer given in the book is wrong\n"
     ]
    }
   ],
   "source": [
    "#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",
    "h=6.63*10**-34;    #plank's constant(Js)\n",
    "lamda=6928*10**-10;    #wavelength(m)\n",
    "Kb=1.38*10**-23;    #boltzmann constant(J/K)\n",
    "T=291;    #temperature(K)\n",
    "\n",
    "#Calculation\n",
    "delta_E=c*h/lamda;\n",
    "N=math.exp(-delta_E/(Kb*T));    #ratio of population\n",
    "\n",
    "#Result\n",
    "print \"ratio of population is\",round(N*10**32,2),\"*10**-32\"\n",
    "print \"answer given in the book is wrong\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example number 11.6, Page number 11.57"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 26,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "wavelength is 632 *10**-9 m\n"
     ]
    }
   ],
   "source": [
    "#importing modules\n",
    "import math\n",
    "from __future__ import division\n",
    "\n",
    "#Variable declaration\n",
    "Kb=1.38*10**-23;    #boltzmann constant(J/K)\n",
    "T=330;    #temperature(K)\n",
    "delta_E=3.147*10**-19;       #energy(J)\n",
    "c=3*10**8;    #velocity of light(m/sec)\n",
    "h=6.63*10**-34;    #plank's constant(Js)\n",
    "\n",
    "#Calculation\n",
    "lamda=c*h/delta_E;    #wavelength(m)\n",
    "\n",
    "#Result\n",
    "print \"wavelength is\",int(lamda*10**9),\"*10**-9 m\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example number 11.7, Page number 11.58"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 28,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "laser beam divergence is 0.5 *10**-3 radian\n"
     ]
    }
   ],
   "source": [
    "#importing modules\n",
    "import math\n",
    "from __future__ import division\n",
    "\n",
    "#Variable declaration\n",
    "r1=2*10**-3;    #radius(m)\n",
    "r2=3*10**-3;     #radius(m)\n",
    "d1=2;     #distance(m)\n",
    "d2=4;     #distance(m)\n",
    "\n",
    "#Calculation\n",
    "delta_theta=(r2-r1)/(d2-d1);     #laser beam divergence(radian)\n",
    "\n",
    "#Result\n",
    "print \"laser beam divergence is\",delta_theta*10**3,\"*10**-3 radian\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example number 11.8, Page number 11.58"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "ratio of population is 1.127 *10**30\n",
      "answer given in the book is wrong\n"
     ]
    }
   ],
   "source": [
    "#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",
    "h=6.63*10**-34;    #plank's constant(Js)\n",
    "lamda=6943*10**-10;    #wavelength(m)\n",
    "Kb=1.38*10**-23;    #boltzmann constant(J/K)\n",
    "T=300;    #temperature(K)\n",
    "\n",
    "#Calculation\n",
    "new=c/lamda;\n",
    "N=math.exp(h*new/(Kb*T));    #ratio of population\n",
    "\n",
    "#Result\n",
    "print \"ratio of population is\",round(N*10**-30,3),\"*10**30\"\n",
    "print \"answer given in the book is wrong\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example number 11.9, Page number 11.58"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "wavelength is 8632.8 angstrom\n",
      "answer given in the book is wrong\n"
     ]
    }
   ],
   "source": [
    "#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",
    "h=6.63*10**-34;    #plank's constant(Js)\n",
    "Eg=1.44*1.6*10**-19;    #band gap(J)\n",
    "\n",
    "#Calculation\n",
    "lamda=c*h/Eg;     #wavelength(m)\n",
    "\n",
    "#Result\n",
    "print \"wavelength is\",round(lamda*10**10,1),\"angstrom\"\n",
    "print \"answer given in the book is wrong\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example number 11.10, Page number 11.59"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "energy gap is 0.8 eV\n"
     ]
    }
   ],
   "source": [
    "#importing modules\n",
    "import math\n",
    "from __future__ import division\n",
    "\n",
    "#Variable declaration\n",
    "lamda=1.55;     #wavelength(micro m)\n",
    "\n",
    "#Calculation\n",
    "Eg=1.24/lamda;      #energy gap(eV)\n",
    "\n",
    "#Result\n",
    "print \"energy gap is\",Eg,\"eV\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example number 11.11, Page number 11.59"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "coherence length is 12 *10**3 m\n",
      "spectral half width is 4.56 *10**-17 m\n",
      "purity factor is 1.6 *10**10\n"
     ]
    }
   ],
   "source": [
    "#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",
    "tow=4*10**-5;    #time(sec)\n",
    "lamda=740*10**-9;     #wavelength(m)\n",
    "\n",
    "#Calculation\n",
    "L=tow*c;     #coherence length(m)\n",
    "delta_lamda=lamda**2/L;     #spectral half width(m)\n",
    "Q=lamda/delta_lamda;     #purity factor\n",
    "\n",
    "#Result\n",
    "print \"coherence length is\",int(L/10**3),\"*10**3 m\"\n",
    "print \"spectral half width is\",round(delta_lamda*10**17,2),\"*10**-17 m\"\n",
    "print \"purity factor is\",round(Q/10**10,1),\"*10**10\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example number 11.12, Page number 11.59"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "ratio of emissions is 8.4 *10**4\n",
      "answer given in the book is wrong\n"
     ]
    }
   ],
   "source": [
    "#importing modules\n",
    "import math\n",
    "from __future__ import division\n",
    "\n",
    "#Variable declaration\n",
    "new=5.9*10**14;    #frequency(Hz)\n",
    "h=6.63*10**-34;    #plank's constant(Js)\n",
    "Kb=1.38*10**-23;    #boltzmann constant(J/K)\n",
    "T=2500;    #temperature(K)\n",
    "\n",
    "#Calculation\n",
    "R=math.exp(h*new/(Kb*T))-1;     #ratio of emissions\n",
    "\n",
    "#Result\n",
    "print \"ratio of emissions is\",round(R/10**4,1),\"*10**4\"\n",
    "print \"answer given in the book is wrong\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example number 11.13, Page number 11.60"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "beam divergence is 1.02 *10**-4 radian\n"
     ]
    }
   ],
   "source": [
    "#importing modules\n",
    "import math\n",
    "from __future__ import division\n",
    "\n",
    "#Variable declaration\n",
    "lamda=1.06*10**-6;      #wavelength(m)\n",
    "d=2.54*10**-2;     #distance(m)\n",
    "\n",
    "#Calculation\n",
    "theta=2.44*lamda/d;      #beam divergence(radian)\n",
    "\n",
    "#Result\n",
    "print \"beam divergence is\",round(theta*10**4,2),\"*10**-4 radian\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example number 11.14, Page number 11.60"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "number of photons/minute is 4.39 *10**17\n"
     ]
    }
   ],
   "source": [
    "#importing modules\n",
    "import math\n",
    "from __future__ import division\n",
    "\n",
    "#Variable declaration\n",
    "P=2.3*10**-3;    #power(W)\n",
    "c=3*10**8;    #velocity of light(m/sec)\n",
    "h=6.63*10**-34;    #plank's constant(Js)\n",
    "lamda=6328*10**-10;    #wavelength(m)\n",
    "\n",
    "#Calculation\n",
    "n=P*lamda*60/(c*h);      #number of photons/min\n",
    "\n",
    "#Result\n",
    "print \"number of photons/minute is\",round(n/10**17,2),\"*10**17\""
   ]
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "Python 2",
   "language": "python",
   "name": "python2"
  },
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 2
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython2",
   "version": "2.7.9"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 0
}