Astronomy quiz question: finding Mars, Venus (2)

Astronomy 210 Quiz 2, Fall Semester 2010
Cuesta College, San Luis Obispo, CA

Consider Earth, Mars and Venus in their orbits as shown in the diagram below. (This drawing is not to scale, and orbits have been simplified as circles instead of ellipses.)

[Version 1]
What is seen by an observer in San Luis Obispo, CA at sunrise (6 AM)?
(A) Only Venus.
(B) Only Mars.
(C) Both Venus and Mars.
(D) (None of the above choices, as both Venus and Mars would not be visible in the San Luis Obispo, CA sky at this time.)

Correct answer: (B)

At 6 AM, Venus would be below the observer's horizon, while Mars would be visible above the west horizon as the sun rises in the east horizon.

Section 70158
(A) : 10 students
(B) : 8 students
(C) : 3 students
(D) : 1 student

[Version 2]
What is seen by an observer in San Luis Obispo, CA at sunset (6 PM)?
(A) Only Venus.
(B) Only Mars.
(C) Both Venus and Mars.
(D) (None of the above choices, as both Venus and Mars would not be visible in the San Luis Obispo, CA sky at this time.)

Correct answer: (A)

At 6 PM, Mars would be below the observer's horizon, while Venus would be visible above the west horizon as the sun sets in the west horizon.

Section 70158
(A) : 12 students
(B) : 7 students
(C) : 2 students
(D) : 2 students

"Success level": 50% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.55