# hwk4 - 3 Problem B It is observed that α particles with...

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Physics 31: Homework #4 Due Thursday, February 14, 2008 Problem A: A parallel beam of α particles with ±xed kinetic energy is normally incident on a piece of gold foil. (a) If 100 α particles per minute are detected at 20 , how many will be counted at 40, 60, 80, and 100 ? (b) If the kinetic energy of the incident α particles is doubled, how many scattered α particles will be observed at 20 ? (c) If the original α particles were incident on a copper foil of the same thickness, how many scattered α particles would be detected at 20 ? The density of copper is 8.9 gm/cm 3 , and the density of gold is 19.3 gm/cm
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Unformatted text preview: 3 . Problem B: It is observed that α particles with kinetic energies of 13.9 MeV and higher, incident on copper foils, do not obey Rutherford’s [sin( θ/ 2)] 4 law. Estimate the nuclear size of copper from this observation, assuming that the Cu nucleus remains ±xed in a head on collision with an α particle. Problem C: Draw an energy level diagram for the Li ++ ion, for which Z = 3. Problem D: What is the radius of the ±rst Bohr orbit in (1) He + , (b) Li ++ , and (c) Be +++ ? Do the following problems in Beiser: Chapter 3: 32, 35 Chapter 4: 6, 16, 20, 22...
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## This note was uploaded on 02/29/2008 for the course PHYSICS 31 taught by Professor Hickman during the Spring '07 term at Lehigh University .

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