Lecture06

Lecture06 - Lecture6 Jan.23 Quan0za0on

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Unformatted text preview: Lecture6 Jan.23 Quan0za0on h4p://www.noao.edu/image_gallery/html/im0600.html iclickerQuiz(Jan.20) Anelectronhasamomentumequalto1 MeV/c.Whatisitstotalenergy? A) 0.56MeV B) 1.12MeV C) 2.24MeV E= (1MeV ) 2 + ( 0.511MeV ) 2 me=0.511MeV/c2 DiscoveryoftheElectron J.J.Thomson 1896 CrossedEandBfields: Crooke'svacuumtube Cathoderaytube(CRT) qvB = qE E v= B RayDeflec0on: v2 qvB = m R q v E = = 2 = const. m BR B R 2008by W.H. Freeman and Company MillikanOilDropletExperiment qE 1911 mg e=1.6x1019C m=9.11x1031kg 2008by W.H. Freeman and Company BlackBodyRadia0on 2008by W.H. Freeman and Company RayleighJeansLaw 1900 S T ( ) = 2c k BT 4 2008by W.H. Freeman and Company PlanckSpectrum MaxPlanck 1900 c 8 R ( ) = 4 4 exp ( / kBT ) - 1 = hc h=6.64x1034Js 2008by W.H. Freeman and Company LongWavelengthExpansion c 8 R ( ) = 4 4 exp ( / kBT ) - 1 = hc exp ( hc / kBT ) - 1 1 + hc / kBT - 1 = hc / kBT c 8 hc kBT c 8 R ( ) = 4 kT 4 hc 4 4 B 8 ShortWavelengthExpansion c 8 R ( ) = 4 4 exp ( / kBT ) - 1 = hc c 8 R ( ) = 4 4 exp ( / kBT ) - 1 c 8 hc 4 exp ( -hc / kBT ) 4 energydensity exponen0al Boltzmann Factor 9 Wien'sDisplacementLaw maxT = 2.898x10 -3 mK Emax = hc J = 6.86x10 -23 T max K 5kBT kB = 1.381x10 -23 J K 10 StefanBoltzmannLaw dI = R ( ) d I = R ( ) d = T PoweroftheSun: Ts=10,000K As=6x1018m2 I = 10 4 4 = 5.67x10 -8 W m2 K 4 ( ) 4 = 5.67x10 8 W m2 Ps=IA=3.4x1027W MassConversion: PS m = = 4x1010 kg / sec c2 t 11 iclickerQuiz(Jan.23) Ifthetemperatureofablackbodydoubles, bywhatfactordoesthewavelengthatwhich thespectrumisamaximumdecrease? A) 0 B) 1 C) 2 D) 4 ...
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