English Homework for Chapter 1ancient times the rectilinearpropagation oflight was usedto measure theheightofobjectsby comparing thelengthof theirshadows with thelength of theshadowofan objectof known length.A staff2m longwhen held erectcasts a shadowlong,while a buildings shadow is 170m long. How tall is the buildingSolution.According to the law of rectilinear propagation, we get,x=100 (m)So the building is 100m tall.from a water medium with n= is incident upon a water-glass interface at an angleof 45o. The glass index is . What angle does the light make with the normal inthe glassx 2170 3.4Solution.According to the law of refraction, We get,nsin I nsin I 1.33sin 45n=45osin I1.50.626968I38.8I So the light makewith the normal in the glass.n=3. A goldfishswims 10cm from the sideof a sphericalbowl ofwater ofradius20cm.Where does the fish appear to be Does it appear larger or smallerSolution.According to the equation.nnnnl Alrand n =1 , n=, r=-20we can get1nn n1.330.33llr100.116520l8.5836(cm)nl8.58361.331n l1 101.1416So the fish appears larger.R1 =20cmR2=-20cmA-10cmobject is located 2cm to the left of convex end of a glass rod which has a radiusof curvature of 1cm. The index of refraction of the glass is n=. Find the imagedistance.Solution.Refer to the figure. According to the equationnnnnllrand n=1, n =, l 1=-2cm, r1=1cm , we get1.51.511r=1cm01l 112l1Al2d l1- l 1=2cml22cmAl 2English Homework for Chapter 2object 1cm highis 30cm in front ofa thin lens with a focal lengthof 10cm. Whereis the image Verify your answer by graphical construction of the image.Solution.According to the Gausss equation,f =10cm1 1llfand l=-30cm f=10 cm.y=1cmwe getf l10(30)15(cm)- l =30cmll10(30)fOthers are omitted.lens is known to have a focal length of 30cm in air. An object is placed 50cm tothe left of the lens. Locate the image and characterize it.Solution.According to Gausss equation,1 1llf andf =30cml =-50cmf l30(50)ll 30(75( cm)we getf50)l751.5l50The image is a real, larger one.f =30cm- l =50cmobjectistransparentcube, 4mmacross,placed60cm infrontof 20cm focallength.Calculatethe transverseand axialmagnificationand describewhat the image lookslikeSolution.From Gausss equation,we findforthe rearsurfaceof the cube (thefacecloser to the lens)l1 f(60)(20)30( cm)l1that,l1f(60)20For the front surface (the face farther away from the lens),(60.4)2029.9(cm)l260.420300.5The transverse magnification for the rear surface isM t60l3029.9But the axial magnification isM a600.25l( 60.4)SinceM tM a ,the cube doesnt look like a cube.biconvex lens is made out of glass of n=. If one surface has twice the radius ofcurvature of the other, and if the focal length is 5cm, what are the two radiiSolution. Supposing r1= -2r2 ( 2=-2 1),according to the lens equation12 )( n1)(12 ) we get,(1.52 1)( 1r 1-r5210.128220.2564r 1=(cm) r 2=(cm)返回English Homework for Chapter 41. A stop 8mm in diameter is placed halfway between an extended object and alarge-diameterlensof9cm focallength.The lensprojectsan image of the objectonto a screen 14cm away. What is the diameter of the exit pupilLensStopObjectImage- llSolution.