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+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Chapter 23:Optical Devices"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Ex23.1:pg-1094"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "The focal length of the reading glasses is f= 37.5  cm\n"
+     ]
+    }
+   ],
+   "source": [
+    "  #Example 23_1\n",
+    " \n",
+    "  \n",
+    "#To find the focal length of the reading glasses\n",
+    "d1=25.0       #units in cm\n",
+    "d2=-75        #units in cm\n",
+    "f=(d1*d2)/(d2+d1)     #Units in cm\n",
+    "print \"The focal length of the reading glasses is f=\",round(f,2),\" cm\"\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Ex23.2:pg-1094"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "The focal length of the corrective lens is f= 50.0  cm\n"
+     ]
+    }
+   ],
+   "source": [
+    "  #Example 23_2\n",
+    " \n",
+    "  \n",
+    "  #To find the focal length of the corrective lens\n",
+    "d1=-50.0           #units in cm\n",
+    "f=-(d1)         #Units in cm\n",
+    "print \"The focal length of the corrective lens is f=\",round(f),\" cm\"\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Ex23.3:pg-1095"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {
+    "collapsed": false
+   },
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "The combined focal length is= 0.3  cm\n"
+     ]
+    }
+   ],
+   "source": [
+    "  #Example 23_3\n",
+    " \n",
+    "  \n",
+    "#To find the focal length of the combination\n",
+    "d1=20.0            #units in cm\n",
+    "d2=-30.0             #units in cm\n",
+    "d3=60.0           #units in cm\n",
+    "p1=100/d1         #units in dipoters\n",
+    "p2=100/d2         #units in dipoters\n",
+    "p3=100/d3         #units in dipoters\n",
+    "p=1/(p1+p2+p3)          #Units in diopters\n",
+    "print \"The combined focal length is=\",round(p,1),\" cm\"\n"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 2",
+   "language": "python",
+   "name": "python2"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 2
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython2",
+   "version": "2.7.11"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 0
+}