Astronomy quiz question: stars moving away from/toward Earth

Astronomy 210 Quiz 4, spring semester 2011
Cuesta College, San Luis Obispo, CA

[Version 1]
Stars moving away from Earth have:
(A) very small parallax angles.
(B) very large parallax angles.
(C) red-shifted absorption lines.
(D) blue-shifted absorption lines.

Correct answer: (C)

Light from a star moving away from Earth would have wavelengths stretched out because of the Doppler shift, which would shift absorption lines towards slightly larger values ("red-shifted").

Section 30674
(A) : 10 students
(B) : 6 students
(C) : 20 students
(D) : 1 student
(No response) : 1 student

"Success level": 50% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.96
Exam code: quiz04nK4n

[Version 2]
Stars moving toward Earth have:
(A) very small parallax angles.
(B) very large parallax angles.
(C) red-shifted absorption lines.
(D) blue-shifted absorption lines.

Correct answer: (D)

Light from a star moving towards Earth would have wavelengths scrunched up because of the Doppler shift, which would shift absorption lines towards slightly smaller values ("blue-shifted").

Section 30676
(A) : 4 students
(B) : 10 students
(C) : 8 students
(D) : 19 students

"Success level": 49% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.82
Exam code: quiz04s0sO