## 20120319

### Astronomy quiz question: apparent vs. absolute magnitude

Astronomy 210 Quiz 4, spring semester 2012
Cuesta College, San Luis Obispo, CA

[Version 1]
Bellatrix is a star that is located 77 parsecs away from Earth. If Bellatrix were moved to a location 10 parsecs away, its apparent magnitude m would __________, while its absolute visual magnitude Mv￼ would __________.
(A) get dimmer; not change.
(B) get brighter; not change.
(C) not change; get dimmer.
(D) not change; get brighter.

The apparent magnitude of Bellatrix, which is the brightness as seen from Earth, will get brighter as it is moved closer from 77 parsecs to 10 parsecs. The absolute visual magnitude, which is the intrinsic brightness, will remain the same no matter where Bellatrix is located.

Section 30674
Exam code: quiz04noR3
(A) : 3 students
(B) : 21 students
(C) : 1 student
(D) : 7 students

"Success level": 69% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.69

[Version 2]
Tau Ceti is a star that is located 3.7 parsecs away from Earth. If Tau Ceti were moved to a location 10 parsecs away, its apparent magnitude m would __________, while its absolute visual magnitude Mv￼ would __________.
(A) get dimmer; not change.
(B) get brighter; not change.
(C) not change; get dimmer.
(D) not change; get brighter.

The apparent magnitude of Tau Ceti, which is the brightness as seen from Earth, will get dimmer as it is moved farther away from 3.7 parsecs to 10 parsecs. The absolute visual magnitude, which is the intrinsic brightness, will remain the same no matter where Tau Ceti is located.

Section 30676
Exam code: quiz04sLO8
(A) : 28 students
(B) : 1 student
(C) : 6 students
(D) : 0 students

"Success level": 82% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.40

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