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midterm1-081

# midterm1-081 - PHYS 320 Spring 2008 Midterm Test 4:00 pm...

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PHYS 320 Spring 2008 Midterm Test 3/3/08 @ 4:00 pm 1 SOLUTIONS 1. Complete the table below by entering the particles (photon, electron, or N/A) that initiate and result from the processes listed, indicate if the process is elastic, inelastic, or not applicable. Give a brief description of Photoelectric effect Experiment In Out Type of scattering Compton Scattering photon Photon + e - Inelastic Electron interference electron electron Elastic Photoelectric effect photon electron Inelastic. Blackbody radiation N/A photon N/A X-ray diffraction photon photon Elastic Note: if you thought that by X-ray diffraction we mean creation of high-energy photons (electrons in – photons out), and not a diffraction of photons from a crystal, your answer is also counted as correct. Photoelectric effect: Photons hit a target and eject electrons. Energy of a photon is transmitted to an electron. Part of this energy is spent to overcome the barrier (metal work function) and the rest is kinetic energy of the ejected electron: E photon = E K + φ 2. A positron moving to the right and an electron moving to the left, each with kinetic energy of 10 MeV, collide and annihilate. As a result of the annihilation two identical photons are created and fly apart (up and down). Find with 4 significant figures the following: a) velocity of the electron before collision (in terms of speed of light), and b) energy and wavelength of the photon moving up. 2 2 e+ 2 2 10 0.511 10.511 MeV 10 0.511 10.511 MeV 10.511 10.511 21.022 MeV 10.511 20.57 0.511 1 1 0.9988 0.9988 21.022 MeV 10.51 Me 22 eK e e tot e e e e e e e tot photon EE m c m c EEE E mc u uc c E E γ + +− + + + + =+ = + = = + = =+= + = == = =− = = = 4 6 V 1240 eV nm 1.180 10 nm 10.511 10 eV photon photon hc E λ = × ×

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PHYS 320 Spring 2008 Midterm Test 3/3/08 @ 4:00 pm 2 3. X-rays are created in a cathode ray tube with an anode from cobalt (Co) under applied voltage of 5000 V.
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midterm1-081 - PHYS 320 Spring 2008 Midterm Test 4:00 pm...

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