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Unformatted text preview: PHY-2054C-002, Fall 2008 Instructor: Dr. Bhattacharya Quiz #11 (KEY), Thursday, Dec 4 1. The expression for the relativistic kinetic energy is given by K= mc2 1- v 2 /c2 - mc2 . The speed of a particle whose kinetic energy is equal to its rest energy is (a) (b) (c) (d) (e) c 2c 0.5c 0.866 c 0
2 explanation: K = mc 2 v= 3 c 2 1-v /c2 - mc2 = mc2 , or, 1/ 1 - v 2 /c2 = 2, from which it follows = 0.866c. 2. In Bohr's model of the Hydrogen atom the expression for the energy levels is given by 1 En = -13.6eV 2 n Therefore, according to this model if an electron jumps from n=1 energy level to n = 2 energy level, it (a) absorbs a photon of energy 13.6 eV (b) emits a photon of energy 13.6 eV (c) absorbs a photon of energy 10.2 eV (d) emits a photon of energy 10.2 eV (e) absorbs a photon of energy 6.8 eV (f) emits a photon of energy 6.8 eV Explanation: The ground state electron needs to absorb energy to get to the excited state (n=2). IN ORDER TO GET CREDIT IN BOTH CASES PLEASE SHOW YOUR WORK ...
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