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+{
+ "metadata": {
+  "name": ""
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "Chapter 11:Lasers"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example 11.1, Page number 11.6"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "\n",
+      "import math\n",
+      "\n",
+      "#Variable declaration\n",
+      "lamda = 6943.*10**-10  #wavelength(m)\n",
+      "T = 300.               #temperature(K)\n",
+      "h = 6.626*10**-34      #Planck's constant\n",
+      "c = 3*10**8            #velocity of light(m/s)\n",
+      "K = 8.61*10**-5\n",
+      "\n",
+      "#Calculations\n",
+      "E2_E1 = (h*c)/(lamda*1.6*10**-19) #in eV\n",
+      "N2_N1 = math.exp(-E2_E1/(K*T))\n",
+      "\n",
+      "#Result\n",
+      "print \"The relative population of two states in a ruby laser is\",round((N2_N1/1E-31),2)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "The relative population of two states in a ruby laser is 8.2\n"
+       ]
+      }
+     ],
+     "prompt_number": 12
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Example 11.2, Page number 11.14"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "\n",
+      "#Variable declaration\n",
+      "a1 = 4.   #diameter of laser beam for distance first(m)\n",
+      "a2 = 6.   # diameter of laser beam from second distance(m)\n",
+      "d1 = 1.   #First distance from laser to output beam spot(m)\n",
+      "d2 = 2.   #Second distance from laser to output beam spot(m)\n",
+      "\n",
+      "#Calculation\n",
+      "D = (a2-a1)/(2*(d2-d1))\n",
+      "\n",
+      "#Result\n",
+      "print \"Divergence =\",D,\"milliradian\""
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "Divergence = 1.0 milliradian\n"
+       ]
+      }
+     ],
+     "prompt_number": 14
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
+\ No newline at end of file