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  "name": "",
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 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "heading",
     "level": 1,
     "metadata": {},
     "source": [
      "Lasers"
     ]
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example number 2.1, Page number 52"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "#To calculate the relative population \n",
      "\n",
      "#importing modules\n",
      "import math\n",
      "\n",
      "#Variable declaration\n",
      "lamda = 590;        #wavelength(nm)\n",
      "h = 6.625*10**-34;       #planck's constant\n",
      "c = 3*10**8;            #velocity of light(m/s)\n",
      "k = 1.38*10**-23;       #boltzmann's constant\n",
      "T = 523;                #temperature(Kelvin)\n",
      "\n",
      "#Calculation\n",
      "lamda = lamda*10**-9;      #wavelength(m)      \n",
      "#n1byn2 = math.exp(-(E2-E1)/(k*T))\n",
      "#but E2-E1 = h*new and new = c/lamda\n",
      "#therefore n1byn2 = math.exp(-h*c/(lamda*k*T))\n",
      "n1byn2 = math.exp(-h*c/(lamda*k*T));\n",
      "\n",
      "#Result\n",
      "print \"relative population of Na atoms is\",n1byn2"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "relative population of Na atoms is 5.36748316686e-21\n"
       ]
      }
     ],
     "prompt_number": 1
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example number 2.2, Page number 53"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "#To calculate the ratio of stimulated to spontaneous emission \n",
      "\n",
      "#importing modules\n",
      "import math\n",
      "\n",
      "#Variable declaration\n",
      "lamda = 590;        #wavelength(nm)\n",
      "h = 6.625*10**-34;       #planck's constant\n",
      "c = 3*10**8;            #velocity of light(m/s)\n",
      "k = 1.38*10**-23;       #boltzmann's constant\n",
      "T = 523;                #temperature(Kelvin)\n",
      "\n",
      "#Calculation\n",
      "lamda = lamda*10**-9;      #wavelength(m)      \n",
      "#n21dashbyn21 = 1/(math.exp(h*new/(k*T))-1)\n",
      "#but new = c/lamda\n",
      "#therefore n21dashbyn21 = 1/(math.exp(h*c/(lamda*k*T))-1)\n",
      "A = math.exp(h*c/(lamda*k*T))-1;\n",
      "n21dashbyn21 = 1/A;    \n",
      "\n",
      "#Result\n",
      "print \"ratio of stimulated to spontaneous emission is\",n21dashbyn21\n",
      "print \"answer given in the book is wrong\""
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "ratio of stimulated to spontaneous emission is 5.36748316686e-21\n",
        "answer given in the book is wrong\n"
       ]
      }
     ],
     "prompt_number": 4
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example number 2.3, Page number 53"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "#To calculate the number of photons emitted \n",
      "\n",
      "#importing modules\n",
      "import math\n",
      "\n",
      "#Variable declaration\n",
      "lamda = 632.8;        #wavelength of laser(nm)\n",
      "h = 6.625*10**-34;       #planck's constant\n",
      "c = 3*10**8;            #velocity of light(m/s)\n",
      "p = 3.147;              #output power(mW)\n",
      "\n",
      "#Calculation\n",
      "p = p*10**-3;          #output power(W)\n",
      "lamda = lamda*10**-9;      #wavelength(m)      \n",
      "new = c/lamda;             #frequency(Hz)\n",
      "E = h*new;                 #energy of each photon(J)\n",
      "Em = p*60;                 #energy emitted per minute(J/min)\n",
      "N = Em/E;                  #number of photons emitted per second\n",
      "\n",
      "#Result\n",
      "print \"number of photons emitted per second is\",N"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "number of photons emitted per second is 6.01183879245e+17\n"
       ]
      }
     ],
     "prompt_number": 5
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [],
     "language": "python",
     "metadata": {},
     "outputs": []
    }
   ],
   "metadata": {}
  }
 ]
}