Astronomy 210 Quiz 2, Fall Semester 2009
Cuesta College, San Luis Obispo, CA
Why does a total lunar eclipse not occur every time the moon is full?
(A) The orbit of the moon is not a perfect circle, but is an ellipse.
(B) The moon rotates such that it always keeps the same side facing Earth.
(C) The orbit of the moon around Earth is tilted with respect to the orbit of Earth around the sun.
(D) The direction of Earth's axis precesses over a 23,000 year cycle.
Correct answer: (C)
When the moon is full, it is on the opposite side of Earth from the sun, but due to its tilted orbit may be either above or below Earth's umbral and penumbral shadow zones, such that there is no (total) lunar eclipse.
Response (A) explains why some solar eclipses are annular rather than total. Response (B) explains why the near side of the moon is constant; response (D) is the reason why Polaris will not always be the pole star.
Section 70158
(A) : 9 students
(B) : 3 students
(C) : 36 students
(D) : 1 student
(blank): 1 student
Success level: 74% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.47
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Astronomy 210 Quiz 2, Fall Semester 2010
Cuesta College, San Luis Obispo, CA
Section 70160
(A) : 8 students
(B) : 2 students
(C) : 27 students
(D) : 2 students
"Success level": 72% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.36
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