First exam review - This is a combined set of lecture notes...

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This is a combined set of lecture notes for Hour Exam 1, Fall 2010. Material will be “marked up” in four different ways: Material marked pink will not be covered . You should just scan through it for background, but need not actually study it well. Material marked blue consists of equations and formulas that will be given to you on a sheet handed out with the test. Material marked yellow is especially important and should be well studied. If it contains formulas or facts they will not be handed out with the test. You should write them of a a “cheat sheet” on one side of an ordinary sheet of paper that you may use during the test. Material marked green will possibly be on the test but will not be used in computation problems, but rather true-false, multiple choice, or fill in the blanks types of problems. It to should, if you deem it necessary, be included on your cheat sheet. Unmarked material is not to be disregarded, but is not as important as yellow material. The homework problems should also be studied.
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Experiments that show Classical Mechanics is wrong 1. Black body radiation (“UV catastrophe”) 2. Heat capacity of crystals at low temperatures 3. Atomic Spectra 4. Photoelectric effect 5. Space quantization of magnetic atoms 6. Direct observation of matter wave diffraction (now known as LEED)
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A “Black Body” is a box with a small hole in it. If hot, it is filled with light, which escapes the hole. The nature of the light depends only on temperature, not material. Classical mechanics predicts that the spectrum of the light inside the cavity (energy per unit frequency interval d ν ) is 2 3 8 ν π ρ c T k d d b = which means the energy density goes to infinity at high frequencies (UV). This derivation assumes that the light is excited modes of oscillations like the waves of sound inside organ pipes, including all harmonics. At the surface of the sun (6000K) one cubic meter of empty space has almost exactly 1 J of energy in it, integrated over all wavelengths . .. it is not infinite!
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The actual spectrum of black body radiation looks like this, and falls off exponentially at high frequencies: The explanation is non-obvious. The dashed line is the incorrect classical prediction at 6000k.
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Classical statistical thermodynamics predicts that the heat capacity per mole of a metal is 3R. This is based on the classical theory of vibrations of solids. It is the same as to the theory of the black body except that it recognizes the finite number of atoms present. Experiment shows that at low temperatures the heat capacity rises from zero at T = 0 as T 3 . At high temperatures it really is 3R. Ratio of real to classical heat capacity Explanation is similarly non-obvious, but same as for black body.
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Rutherford proposed an orbital model of the H atom: electron around proton. Classical mechanics predicts m E e r e E 3 2 0 0 2 2 4 and 8 = = ε ν πε where e is electron charge, m electron mass, and the zero of energy is set for the electron at a large distance from the proton. This predicts that if a proton
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This note was uploaded on 09/22/2011 for the course CHEM 222 taught by Professor Linda during the Spring '11 term at Edmonds Community College.

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First exam review - This is a combined set of lecture notes...

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