M34_KNIG9404_ISM_C34.pdf

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1、34ELECTROMAGNETICFIELDSANDWAVESConceptualQuestions34.1.(a)Yes,up.Andreseesthesamemagneticfieldasthelaboratoryfield,whichpointsup.ddd(b)AndreseesanelectricfieldEAA=×VBLL,whichbytheright-handrulepointsintothepage.34.2.(a)Amagneticforceactingdownandanelectricforceactingup.Sharonsees

2、thesamemagneticfieldasBilldddbutalsoseesanelectricfieldEBB=×VBSS.(Notethatthemagneticandelectricforcesonthechargeareequalandoppositesothetotalforceonthechargeiszero.)(b)InBill’sframeofreferencethechargeisatrestandthereforehasnomagneticforceactingonit.Sincethereisnotanelectricfiel

3、dpresentinBill’sreferenceframe,noforcesactonthecharge.34.3.(a)Negative.Yourthumbwillpointoppositetothemagneticfield.(b)Positive.Yourthumbwillpointinthesamedirectionasthemagneticfield.34.4.Negative.Thenetcurrentthroughthesurfaceistotheright,andifyoucurlyourfingersalongthearrowarou

4、ndthesurface,yourthumbpointstotheleft.dΦe34.5.Decreasing.Pointingthethumbofyourrighthandmakesyourfingerscurlccw,somustbenegativetodtdgetacwB.ddd34.6.(a)No.ThedirectionofvemisE×Bwhichwouldbealongthe−x-axis.(b)Yes.ThePointingvectorrequirementissatisfied.dd34.7.(a)Theright-handruleh

5、asE×Bpointoutofthepage.dd(b)E×Bpointsup.34.8.(a)SinceIE∝2,thenewintensityis40W/m.20(b)ForanelectromagneticwaveE∝B,so40W/m.200(c)Forelectromagneticwaves,doublingoneamplituderequiresthattheotherisdoubled,so40W/m.2(d)Changingthefrequencydoesnotchangetheamplitudesandhencetheintensity

6、isunchangedat10W/m2.34.9.AloopantennaworksbytakingadvantageofthecurrentproducedbymagneticinductioninFaraday’slawasanelectromagneticwavepassesthrough.©Copyright2013PearsonEducation,Inc.Allrightsreserved.Thismaterialisprotectedunderallcopyrightlawsastheycurrentlyexist.Noportionofth

7、ismaterialmaybereproduced,inanyformorbyanymeans,withoutpermissioninwritingfromthepublisher.34-134-2Chapter3434.10.IIIII>=>>.TheintensitypassingthroughapolarizerisIcos2θ.Polarizerdisalignedwiththedceba0incidentwave(0θ=)whileθ=°90forpolarizera.Polarizerscandeareatthesameangleθfromt

8、hevertical.ExercisesandProblemsSection34