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Quiz10_Physics241_S09

Quiz10_Physics241_S09 - how many photons would be emitted...

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Quiz 10- 27 April 2009 Name: o ------+----- J Recitation Da~/Time _ 1. The mass of a muon is 207 times the mass of the electron, and the average lifetime of a muon at rest is 2.20 J.ls. In an accelerator experiment, muons are measured to have an average lifetime of 69.0 J.ls. For the moving muons, find the following: 1. Calculate the wavelength of a photon having an energy of 6.2x10- 15 J. 11. Calculate the wavelength of a photon having a momentum of 3.8 x10- 24 kg.mls. (2 points) . -]4 9 - t~6::.?xjO IJx/o - :;" he..- ? - £ b ~ 2--t' /0 i ~ ..- 3Lf . - 1 '/ {) ,..-. h-- 6~b::)X. if ;1 - ~lf- f ~.~(iO 2. Consider a hypothetical light source that emits light exclusively at a wavelength of 450nm. If electrical energy is supplied at the rate of20W (where 1W = lJ/s), and if the light source is 50% efficient at converting that energy to light, calculate
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Unformatted text preview: how many photons would be emitted during its lifetime of 48 hours. (4 points) [;. . . :::: hf J-~ :::;:: £·63;(10 ~34 x'.!3,-6i--ro2-'. ~/1~ P~VOhV7 ;[ . ~ 1+~4-1 A I(} J 4-,(0)(/0'1 ~ f~72.J( 1/ J 24-.::-~ ·CJ ~ 10 p~lv"'? 3. Light of wavelength 460nm shines on the clean surface of a metal with a work function of2.0 eV. 1. Find the stopping potential for electrons ejected from the metal. 11. Find the maximum speed of the ejected electrons. (4 points) I V ,e. 5lv f := h-l-f = 0J:--;II §j -i 62> X I(j 31; y ,3 l It! '-1 ---,i 9 '-t -6, x. ;0 x IVb 'i 10 fI E = hf=hc/A p= h/A h=6.63 x10-34 1.s !:J.A =h/mc(l-cos¢) eV = 1.6xlO-19 l hf= Km~ +<D 1W=lJ/s = eV stop-t<D C = 3.0 x 10 8 m1s . e = 1.6x10-19 coulomb...
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