Astronomy quiz question: red giant vs. the sun

Astronomy 210 Quiz 5, spring semester 2014
Cuesta College, San Luis Obispo, CA

A red giant is __________ than the sun.
(A) cooler and dimmer.
(B) cooler and brighter.
(C) hotter and dimmer.
(D) hotter and brighter.

Correct answer (highlight to unhide): (B)

From Wien's law, the red giant is cooler than the sun, which is yellow-hot. An H-R diagram is provided with this quiz.


As shown below, all giants would have a luminosity greater than the sun. Thus a red giant must be cooler and brighter than the sun.


The entries for the "box method" of comparing relative Stefan-Boltzmann parameters are listed below.

	Lum.	=	size	×	Temp.4
Red s.g.	↑		↑↑↑		↓
White m.s.	↓		↓↓↓		↑

Section 30674
Exam code: quiz05n3Ne
(A) : 5 students
(B) : 15 students
(C) : 2 students
(D) : 3 students

Success level: 63% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.75

Section 30676
Exam code: quiz05suN7
(A) : 8 students
(B) : 26 students
(C) : 3 students
(D) : 2 students

Success level: 69% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.43