Cuesta College, San Luis Obispo, CA
An astronomy question on an online discussion board[*] was asked and answered:
??: To replace my telescope with a better one, should I buy one with a tube longer than the one I already have, or one with a diameter wider than the one I already have?Discuss why this response is correct. Support your answer using the properties of telescopes and telescope powers.
GG: First priority would be to buy a wider diameter telescope instead of one that is longer.
[*] answers.yahoo.com/question/index?qid=20150925205424AARw53Z
Solution and grading rubric:
- p:
Correct. Discusses how area and diameter of a telescope's primary mirror or lens respectively determines the light-gathering power and resolving power, such that a "wider" diameter telescope would be better to make fainter objects brighter, and allow finer details to be seen; and while the "longer" telescope would have a longer primary mirror/lens focal length and thus better magnification, but this would be a lower priority after improving a telescope's ability to make faint objects with fine details visible. - r:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Correct and complete discussion of two of the three telescope parameters and powers. - t:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Problems with either diagram or discussion. Discussion of only one of the three telescope parameters and powers is correct and complete. - 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. Misconceptions or non-relevant concepts. - y:
Irrelevant discussion/effectively blank. - z:
Blank.
Section 70160
Exam code: midterm01nW6b
p: 3 students
r: 2 students
t: 15 students
v: 9 students
x: 1 student
y: 1 student
z: 0 students
A sample "p" response (from student 4338):
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