gre物理sub题目精选解答

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1、电磁学1.AFastchargedparticlepassesperpendicularlythroughathinglasssheetofindexofrefraction1.5.TheconeofCerenkovlight,emittedintheglassatangleθ,isincidentontheglass-airinterfaceatthecriticalanglefortotalreflection.Whatisthespeedoftheparticle?answer:2.answer:D3

2、.answer:E一些简单的量子力学题：1.Aparticleofchargeeandmassmistrappedinaone-dimentionalsquarewellofwidth2awithimpenetrablewalls.Thewallsarelocatedatx=−aandx=a.(1)Ifthequantummechanicalstatesarelabledbyn(n=1isthegroundstate),whatistheexpectationvalueofx^2forverylargen?

3、answer:a^2/3(2)AsmallelectricfieldofstrengthE_0isappliedinthexdirection.Whatisthechangeoftheenergyofthefirstexcitedstateofthisparticleduetothiselectricfield?(Assumethatthetotalpotential,duetothewallsandtheelectricfield,is0atx=0.)answer:02.Thewavefunctionwh

4、ereAandbarerealconstants,isanormalizedeigenfunctionoftheSchrödingerequationforaparticleofmassMandenergyEinaonedimensionalpotentialV(x)suchthatV(x)=0atx=0.DeterminetheformofthepotentialV(x)answer:3.answer:E统计：1.answer:B2.answer:BA一些简单的粒子物理题和狭义相对论1.Thehalf-l

5、ifeofamesonatrestis2.5×10-8second.Abeamofmesonsisgeneratedatapoint15metersfromadetector.Onlyhalfofthemesonslivetoreachthedetector.Findthespeedofthemesonanswer:2.3.Abeamofparticlesisincidentonathintargetofthicknesst.Ifthecrosssectionpernucleusforascattering

6、oftheparticlesbythenucleioftheofthetargetisσ,andthenumberofnucleiperunitvolumeisn,whatisthefractionofparticlesscattered?answer:ntσ4.Aprotonbeamisincidentonascatterer0.1centimeterthick.Thescatterercontains10^20targetnucleipercubiccentimeter.Inpassingthrough

7、thescatterer,oneprotonperincidentmillionisscattered.Calculatethescatteringcrosssection.answer:10^-25cm^2