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ASSOCIATION OF AMERICAN MEDICAL COLLEGES Sample Items: PHYSICAL SCIENCES (Extracted from MCAT Practice Test 3R ) www.aamc.org/mcat
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Copyright 2003 AAMC. All rights reserved. 2 Passage III (Questions 11-16) When X-rays are produced in an X-ray tube, two types of X-ray spectra are observed: continuous spectra and line spectra. A continuous spectrum is produced by bremsstrahlung, the electromagnetic radiation produced when free electrons are accelerated during collisions with ions. A line spectrum results when an electron having sufficient energy collides with a heavy atom, and an electron in an inner energy level is ejected from the atom. An electron from an outer energy level then fills the vacant inner energy level, resulting in emission of an X-ray photon. For example, if an electron in the n = 1 energy level is ejected from an atom, an electron in the n = 2 level of the atom can fill the vacancy created in the n = 1 level, and a photon with an energy equal to the energy difference between the two levels will be emitted. A scientist produced both types of spectra using the X- ray tube shown in Figure 1 below. Figure 1
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This note was uploaded on 04/17/2008 for the course CHEM 1211 taught by Professor Atwood during the Spring '07 term at University of Georgia Athens.

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pssampleitems - ASSOCIATION OF AMERICAN MEDICAL COLLEGES...

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