PHYS 1160 FINAL EXAM

PHYS 1160 FINAL EXAM
Question 1
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Question text
To study the distribution of interstellar atomic hydrogen (neutral hydrogen) gas in the galaxy
we would use
Select one:
A. an optical telescope and spectrograph to look for emission lines of hydrogen.
B. a radio telescope to look for radiation due to the 21 cm line of hydrogen.
C. an infrared telescope in order to penetrate the dust that obscures much of the Milky
Way.
D. A millimetre wave telescope to look for rotational lines due to hydrogen.
Feedback
B is the correct answer. Neutral atomic hydrogen is detected most easily by its 21cm radio
emission. Rotational lines in the millimetre region are only seen from molecules, and optical
emission lines are only seen where gas is heated by nearby hot stars.
The correct answer is: a radio telescope to look for radiation due to the 21 cm line of
hydrogen.
Question 2
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