{

 "metadata": {

  "name": "",

  "signature": "sha256:141e2987b2be679ae1fc9e807cf81c12805438f836d3be09701fc88866bf9bb5"

 },

 "nbformat": 3,

 "nbformat_minor": 0,

 "worksheets": [

  {

   "cells": [

    {

     "cell_type": "heading",

     "level": 1,

     "metadata": {},

     "source": [

      "Chapter5:LASERS"

     ]

    },

    {

     "cell_type": "heading",

     "level": 2,

     "metadata": {},

     "source": [

      "Ex5.1:pg-164"

     ]

    },

    {

     "cell_type": "code",

     "collapsed": false,

     "input": [

      "import math\n",

      "#to calculate area of the spot on the moon\n",

      "lamda=6*10**-7 #wavelength in m\n",

      "d=2 #diameter in m\n",

      "dtheta=lamda/d #angular spread in radian\n",

      "D=4*10**8 #distance of the moon\n",

      "A=(D*dtheta)**2\n",

      "print \"the areal spread is A=\",\"{:.2e}\".format(A),\"m**2\"\n"

     ],

     "language": "python",

     "metadata": {},

     "outputs": [

      {

       "output_type": "stream",

       "stream": "stdout",

       "text": [

        "the areal spread is A= 1.44e+04 m**2\n"

       ]

      }

     ],

     "prompt_number": 11

    },

    {

     "cell_type": "heading",

     "level": 2,

     "metadata": {},

     "source": [

      "Ex5.2:pg-164"

     ]

    },

    {

     "cell_type": "code",

     "collapsed": false,

     "input": [

      "import math\n",

      "#to calculate angular spread of the beam\n",

      "lamda=8*10**-7 #wavelength in m\n",

      "d=5*10**-3 #aperture in m\n",

      "dtheta=lamda/d \n",

      "print \"the angular spread of the beam is dtheta=\",\"{:.1e}\".format(dtheta),\"radian\"\n",

      "#to calculate the areal spread when it reaches the moon\n",

      "D=4*10**8 #distance of the moon in m\n",

      "A=(D*dtheta)**2\n",

      "print \"the areal spread is A=\",\"{:.3e}\".format(A),\"m**2\"\n"

     ],

     "language": "python",

     "metadata": {},

     "outputs": [

      {

       "output_type": "stream",

       "stream": "stdout",

       "text": [

        "the angular spread of the beam is dtheta= 1.6e-04 radian\n",

        "the areal spread is A= 4.096e+09 m**2\n"

       ]

      }

     ],

     "prompt_number": 10

    },

    {

     "cell_type": "heading",

     "level": 2,

     "metadata": {},

     "source": [

      "Ex5.3:pg-165"

     ]

    },

    {

     "cell_type": "code",

     "collapsed": false,

     "input": [

      "import math\n",

      "#to calculate number of oscillations corresponding to the coherence length\n",

      "L=2.945*10**-2 #coherence length in m\n",

      "lamda=5890*10**-10 #wavelength of sodium light in m\n",

      "n=L/lamda\n",

      "print \"the number of oscillations is n=\",\"{:.1e}\".format(n),\"unitless\"\n",

      "#to calculate coherence time\n",

      "c=3*10**8 #light speed in m\n",

      "Time=L/c #coherence time\n",

      "print \"the coherence Time=\",\"{:.2e}\".format(Time),\"s\"\n"

     ],

     "language": "python",

     "metadata": {},

     "outputs": [

      {

       "output_type": "stream",

       "stream": "stdout",

       "text": [

        "the number of oscillations is n= 5.0e+04 unitless\n",

        "the coherence Time= 9.82e-11 s\n"

       ]

      }

     ],

     "prompt_number": 7

    },

    {

     "cell_type": "heading",

     "level": 2,

     "metadata": {},

     "source": [

      "Ex5.4:pg-165"

     ]

    },

    {

     "cell_type": "code",

     "collapsed": false,

     "input": [

      "import math\n",

      "#to calculate area and intensity of the image\n",

      "lamda=7200*10**-10 #wavelength in m\n",

      "d=5*10**-3 #aperture in m\n",

      "dtheta=lamda/d #angular spread in radian \n",

      "f=0.1 #focal length in m\n",

      "arealspread=(dtheta*f)**2\n",

      "print \"areal spread =\",\"{:.3e}\".format(arealspread),\"m**2\"\n",

      "power=50*10**-3\n",

      "I=power/arealspread\n",

      "print \"intensity of the image is I=\",\"{:.3e}\".format(I),\"watts/m**2\"\n"

     ],

     "language": "python",

     "metadata": {},

     "outputs": [

      {

       "output_type": "stream",

       "stream": "stdout",

       "text": [

        "areal spread = 2.074e-10 m**2\n",

        "intensity of the image is I= 2.411e+08 watts/m**2\n"

       ]

      }

     ],

     "prompt_number": 4

    },

    {

     "cell_type": "code",

     "collapsed": false,

     "input": [],

     "language": "python",

     "metadata": {},

     "outputs": []

    }

   ],

   "metadata": {}

  }

 ]

}