Astronomy quiz question: moon phase, six hours later?

Astronomy 210 Quiz 1, spring semester 2014
Cuesta College, San Luis Obispo, CA

The moon is in its first quarter phase at 3:00 PM. Which phase will the moon have six hours later, at 9:00 PM? Clearly circle your answer below.


Correct answer (highlight to unhide): (F)

The moon takes approximately four weeks (a "moonth") to go through its eight phases, such that it will take approximately one week to go through two phases, or approximately three-and-a-half days to go from one phase to the next phase. Thus the moon in its first quarter phase will still be in the same phase six hours later.

Section 30674
Exam code: quiz01nYe3
(A) : 3 students
(B) : 5 students
(C) : 2 students
(D) : 1 student
(E) : 0 students
(F) : 18 students
(G) : 1 student
(H) : 0 students

Success level: 60% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.48

Section 30676
Exam code: quiz01SLo3
(A) : 6 students
(B) : 12 students
(C) : 1 student
(D) : 4 student
(E) : 2 students
(F) : 18 students
(G) : 2 students
(H) : 0 students

Success level: 42% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.75