Cuesta College, San Luis Obispo, CA
Consider the following statement: "If two stars have the same brightness, the star with the lower temperature will be smaller." Discuss whether this statement is true or not, and support your answer using Wien's law and/or the Stefan-Boltzmann law.
Solution and grading rubric:
- p:
Correct. Discusses how the Stefan-Boltzmann law (luminosity (brightness) proportional to size×Temp4) explains that two stars can have the same brightness if the smaller star is hotter, and the larger star is cooler. - r:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. - t:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. At least recognizes that the Stefan-Boltzmann law is applicable, but argument is garbled. - v:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. - x:
Implementation/application of ideas, but credit given for effort rather than merit. Agrees or disagrees with statement with no discussion. - y:
Irrelevant discussion/effectively blank. - z:
Blank.
Section 30676
p: 38 students
r: 6 students
t: 5 students
v: 7 students
x: 0 students
y: 0 students
z: 1 student
A sample "p" response (from student 2881):
Another sample "p" response (from student 4489), utilizing a "box" method to compare the blackbody properties of two stars:
Another sample "p" response (from student 5659), using an "obvious" explanation:
A sample "p" response (from student 6615) using a variation of the box method:
A sample "p" response (from student 5065) that uses a H-R diagram:
A sample "p" response (from student 0321) that claims that this was subject was not discussed in class, and yet manages to deduce the correct answer:
A sample "r" response (from student 4498) that garbles the box analysis somewhat:
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