Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problems 23.57, 24.29
The Foldscope is a low-cost "origami-based paper microscope"[*] designed by Stanford University researchers to be used for science, medicine, and education in developing countries.[**] It has a single converging lens that can either project an enlarged real image on a screen, or be used as a simple magnifier. When used as a projector, the object distance and image distances are 0.24 mm and 100.00 mm, respectively. When used as a simple magnifier, determine whether or not it is plausible that the angular magnification obtained with this Foldscope could be as high as the stated value of 1,140×. (Use the nominal value of 250 mm for the near point.) Show your work and explain your reasoning.
[*] "MAG (angular magnification) = 1,140×," arxiv.org/pdf/1403.1211v1.pdf.
Solution and grading rubric:
Correct. Determines (a) the focal length of the lens using the thin lens equation, and (b) the resulting angular magnification when used as a simple magnifier, which is slightly less (1,044×) than the stated value (1,140×). May either argue that claim is plausible or implausible with these values.
Nearly correct, but includes minor math errors.
Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. At least has focal length of lens, but compares linear magnification of projected real image instead of angular magnification of virtual image when used as a simple magnifier.
Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner.
Implementation of ideas, but credit given for effort rather than merit. Use of other optics equations, etc.
Irrelevant discussion/effectively blank.
Sections 30882, 30883
Exam code: midterm01b0w7
p: 29 students
r: 2 students
t: 4 students
v: 6 students
x: 0 students
y: 0 students
z: 0 students
A sample "p" response (from student 7810):
Another sample "p" response (from student 2419):