Astronomy quiz question: full Moon rising/setting

Astronomy 10 Quiz 2, Fall Semester 2007
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q2.2

[Version 1]

[3.0 points.] Consider the view of the western horizon shown below, as seen from San Luis Obispo, CA at a certain time of day (or night). Carefully note the position and phase of the Moon in its full phase.


Which one of the following choices best describes time of day (or night) that an observer in San Luis Obispo, CA will see the view shown above?
(A) Just before sunrise.
(B) Just after sunrise.
(C) Just before sunset.
(D) Just after sunset.
(E) (It is not possible to determine the time of day for the view shown above, unless more information is given.)

Correct answer: (A)

The full Moon sets in the west just as the sun rises (in the east). Since the Moon is just above the western horizon, before setting, then this must be just before the sun rises from the east horizon.

Student responses
Section 0135
(A) : 7 students
(B) : 1 student
(C) : 7 students
(D) : 4 students
(E) : 0 students

Section 1073
(A) : 7 students
(B) : 5 students
(C) : 8 students
(D) : 3 students
(E) : 4 students

[Version 2]

[3.0 points.] Consider the view of the western horizon shown below, as seen from San Luis Obispo, CA at a certain time of day (or night). Carefully note the position and phase of the Moon in its full phase.


Which one of the following choices best describes time of day (or night) that an observer in San Luis Obispo, CA will see the view shown above?
(A) Just before sunrise.
(B) Just after sunrise.
(C) Just before sunset.
(D) Just after sunset.
(E) (It is not possible to determine the time of day for the view shown above, unless more information is given.)

Correct answer: (D)

The full Moon rises in the east just as the sun sets (in the west). Since the Moon is just above the eastern horizon, after rising, then this must be just after the sun has set in the west horizon.

Student responses
Section 0135
(A) : 3 students
(B) : 3 students
(C) : 2 students
(D) : 11 students
(E) : 1 student

Section 1073
(A) : 3 students
(B) : 4 students
(C) : 5 students
(D) : 10 students
(E) : 0 students

Interesting to note that students had a lower success rate in answering the version with the sun about to set in the west, compared to the version with the sun just after rising in the east.