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Unformatted text preview: ASTR 302: Stars and Galaxies Dr. Keller Midterm Exam February 1, 2008 Name: ANSWER KEY FOR SHORT ANSWER PROBLEMS _______________________________________________________ Complete the 9 multiple choice and 4 short answer problems attached. Point totals are listed for each problem. Complete all answers on the sheets provided. Be sure to show all of your work. 1) (25 pts) Imagine that the light from a hot, dense object passes through a cool, diffuse cloud of hydrogen gas and then through a prism. Assume that the astronomical objects are widely separated in space. a) (4 pts) Describe the type of spectrum would you expect to see? You would expect to see an absorption spectrum in which the hot dense object provides a continuous spectrum but the cool, diffuse cloud of hydrogen gas absorbs specific wavelengths of light, creating dark bands in the spectrum. b) (6 pts) How would the spectrum be different if the temperature of the hot dense light source was increased? Explain your reasoning. If the temperature of the hot dense light source was increase, the peak wavelength of the absorption spectrum would be shifted to a shorter wavelength (Wien’s Law) and the overall intensity of the continuous part of the spectrum would increase (Stefan Boltzmann Law). The absorption lines from the cool diffuse cloud would not be affected. c) (6 pts) How would the spectrum be different if the temperature of the cloud was increased? Explain your reasoning. If the temperature of the cloud was increased, the width of the absorption lines would increase due to doppler or thermal broadening. The gas molecules would be moving more quickly and the light that is...
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This note was uploaded on 04/03/2008 for the course ASTRONOMY 302 taught by Professor Keller during the Winter '08 term at Cal Poly.
- Winter '08