Astronomy 210 Quiz 6, Fall Semester 2009
Cuesta College, San Luis Obispo, CA
Why is only a small portion of the entire Milky Way visible to the naked eye?
(A) The finite speed of light.
(B) Gas and dust block visual wavelengths.
(C) There is too much dark matter.
(D) Distant stars are receding faster than the speed of light.
Correct answer: (B)
Approximately 1% of the entire Milky Way disk visible to the naked eye, due to the presence of interstellar matter that blocks visual wavelengths. Longer wavelengths of light such as infrared and radio waves do make it through this interstellar matter, allowing a map of the spiral arm structure of the Milky Way to be constructed from IR and radio telescope observations.
Section 70158
(A) : 0 students
(B) : 39 students
(C) : 2 students
(D) : 0 students
Success level: 94% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.10
Section 70160
(A) : 4 students
(B) : 35 students
(C) : 0 students
(D) : 2 students
Success level: 87% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.30
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