{
 "metadata": {
  "name": ""
 },
 "nbformat": 3,
 "nbformat_minor": 0,
 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "heading",
     "level": 1,
     "metadata": {},
     "source": [
      "Chapter 4: Lasers"
     ]
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 4.6.1, Page number 4-7"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\n",
      "#Variable declaration\n",
      "P = 3.147*10**-3     #output power(W)\n",
      "t = 60               #time(sec)\n",
      "lamda = 632.8*10**-9 #wavelength(m)\n",
      "h = 6.63*10**-34     #Planc's constant(J-s)\n",
      "c = 3*10**8          #velocity of light(m/s)\n",
      "\n",
      "#Calculations\n",
      "N = (P*t*lamda)/(h*c)\n",
      "\n",
      "#Result\n",
      "print \"No. of photons emittd each minute is\",round(N/1e+17),\"*10^17\""
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "No. of photons emittd each minute is 6.0 *10^17\n"
       ]
      }
     ],
     "prompt_number": 2
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 4.6.2, Page number 4-7"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\n",
      "import math\n",
      "\n",
      "#Variable declaration\n",
      "T = 300              #temperature(K)\n",
      "lamda = 694.3*10**-9 #wavelength(m)\n",
      "h = 6.63*10**-34     #Planc's constant(J-s)\n",
      "c = 3*10**8          #velocity of light(m/s)\n",
      "k = 1.38*10**-23     #Boltman's constant(J/K)\n",
      "\n",
      "#Calculations\n",
      "N2_by_N1 = math.exp((-h*c)/(lamda*k*T))\n",
      "                    \n",
      "#Result\n",
      "print \"Ratio of population =\",round(N2_by_N1/1e-31,3),\"*10^-31\""
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Ratio of population = 8.874 *10^-31\n"
       ]
      }
     ],
     "prompt_number": 4
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Example 4.6.3, Page number 4-8"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\n",
      "#Variable declaration\n",
      "P = 100*10**3        #output power(W)\n",
      "t = 20*10**-9        #time(sec)\n",
      "N = 6.981*10**15     #no. of photons\n",
      "h = 6.63*10**-34     #Planc's constant(J-s)\n",
      "c = 3*10**8          #velocity of light(m/s)\n",
      "\n",
      "#Calculations\n",
      "lamda = (N*h*c)/(P*t)\n",
      "\n",
      "#Result\n",
      "print \"Wavelength =\",round(lamda/1e-10),\"A\""
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "Wavelength = 6943.0 A\n"
       ]
      }
     ],
     "prompt_number": 8
    }
   ],
   "metadata": {}
  }
 ]
}