PROBLEM 41 &amp; 42 May 18 2010

PROBLEM 41 &amp; 42 May 18 2010 - o a m e c 2 b m e c...

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Solving Problems 41 and 42 Physics 002C May 18, 2010 Problem 41. (Like problem 28.13) What is the maximum current that would be emitted from a copper surface (work function = 4.70 eV) illuminated by 1 W of 243 nm light? a) 0.2 A; b) 0.4 A; c) 0.6 A; d) 0.8 A; e) 1.0 A. What do you know? The number of photons per second is 19 1 6 19 6 10 6 . 1 1 7 . 4 1 / 10 6 . 1 1 7 . 4 1 s eV J eV W dt dN . Each photon releases at most 1 electron of charge e = 1.6 10 -19 C. The maximum current is then A s C s C dt dN e 2 . 0 7 . 4 1 10 6 . 1 1 7 . 4 1 10 6 . 1 6 19 1 6 19 . Problem 42. (Like problem 28.15) What is the energy of an annihilation photon [energy equal to m e c 2 ] after Compton scattering twice through 90
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Unformatted text preview: o ? a) m e c 2 ; b) m e c 2 /2; c) m e c 2 /3; d) m e c 2 /4; e) m e c 2 /5. What do you know? An annihilation photon (from electron-positron pair annihilation) has a wavelength equal to the Compton wavelength. After scattering the first time the wavelength is C C C 2 ) cos 1 ( ' . After the second scattering the wavelength is C C C C C 3 2 ) cos 1 ( 2 ' . The final energy is 2 3 1 3 1 3 ' mc hc hc hc C C ....
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This note was uploaded on 09/23/2010 for the course PH 02c taught by Professor Mile during the Spring '04 term at Riverside Community College.

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