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   "source": [
    "# Chapter 7:LASERS "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example 7.1, Page number 7.32"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Divergence = 0.5 *10**-3 radian\n"
     ]
    }
   ],
   "source": [
    "import math\n",
    "from __future__ import division\n",
    "\n",
    "#variable declaration\n",
    "r1 = 2;                #in radians\n",
    "r2 = 3;                #in radians\n",
    "d1 = 4;                #Converting from mm to radians\n",
    "d2 = 6;                #Converting from mm to radians\n",
    "\n",
    "#calculations\n",
    "D = (r2-r1)/(d2*10**3-d1*10**3)   #Divergence\n",
    "\n",
    "#Result\n",
    "print \"Divergence =\",round(D*10**3,3),\"*10**-3 radian\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example 7.2, Page number 7.32"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Frequency (V) = 4.32 *10**14 Hz\n",
      "Relative Population= 1.081 *10**30\n"
     ]
    }
   ],
   "source": [
    "import math\n",
    "from __future__ import division\n",
    "\n",
    "#variable declaration\n",
    "C=3*10**8                    #The speed of light\n",
    "Lamda=6943                   #Wavelength\n",
    "T=300                        #Temperature in Kelvin\n",
    "h=6.626*10**-34              #Planck constant \n",
    "k=1.38*10**-23               #Boltzmann's constant\n",
    "\n",
    "#Calculations\n",
    "\n",
    "V=(C)/(Lamda*10**-10)       #Frequency\n",
    "R=math.exp(h*V/(k*T))       #Relative population\n",
    "\n",
    "#Result\n",
    "print \"Frequency (V) =\",round(V/10**14,2),\"*10**14 Hz\"\n",
    "print \"Relative Population=\",round(R/10**30,3),\"*10**30\"\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example 7.3, Page number 7.32"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      " Frequency= 4.74 *10**14 Hz\n",
      "no.of photons emitted= 7.322 *10**15 photons/sec\n",
      "Power density = 2.3 kWm**-2\n"
     ]
    }
   ],
   "source": [
    "import math\n",
    "from __future__ import division\n",
    "\n",
    "#variable declaration\n",
    "C=3*10**8                     #Velocity of light\n",
    "W=632.8*10**-9                #wavelength\n",
    "P=2.3\n",
    "t=1\n",
    "h=6.626*10**-34              #Planck constant \n",
    "S=1*10**-6\n",
    "\n",
    "#Calculations\n",
    "V=C/W                        #Frequency\n",
    "n=((P*10**-3)*t)/(h*V)       #no.of photons emitted\n",
    "PD=P*10**-3/S                #Power density\n",
    "\n",
    "#Result\n",
    "print \"Frequency=\",round(V/10**14,2),\"*10**14 Hz\"\n",
    "print \"no.of photons emitted=\",round(n/10**15,3),\"*10**15 photons/sec\"\n",
    "print \"Power density =\",round(PD/1000,1),\"kWm**-2\"\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example 7.4, Page number 7.33"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Wavelenght = 8628.0 Angstrom\n"
     ]
    }
   ],
   "source": [
    "import math\n",
    "from __future__ import division\n",
    "\n",
    "#variable declaration\n",
    "h=6.626*10**-34              #Planck constant \n",
    "C=3*10**8                    #Velocity of light\n",
    "E_g=1.44                     #bandgap \n",
    "\n",
    "#calculations\n",
    "lamda=(h*C)*10**10/(E_g*1.6*10**-19)       #Wavelenght\n",
    "\n",
    "#Result\n",
    "print \"Wavelenght =\",round(lamda),\"Angstrom\"\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "##Example 7.5, Page number 7.33"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Band gap = 0.8 eV\n"
     ]
    }
   ],
   "source": [
    "import math\n",
    "from __future__ import division\n",
    "\n",
    "#variable declaration\n",
    "W=1.55                       #wavelength\n",
    "\n",
    "#Calculations\n",
    "E_g=(1.24)/W                 #Bandgap in eV           \n",
    "\n",
    "#Result\n",
    "print \"Band gap =\",E_g,\"eV\""
   ]
  }
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