Cuesta College, San Luis Obispo, CA
An inexpensive magnifying glass mounted in a shoebox is used with a smartphone as a light source to project images on a wall in a darkened room.[*] Shown at right is a view of the enlarged, upright image of the smartphone inside the projector when looking through the magnifying glass. Discuss what adjustments must be made (if any) to the location and/or orientation of the smartphone in order to properly display an enlarged, upright image on a wall. Show your work and explain your reasoning by using the properties of lenses, thin lens equations and/or ray tracings.
Solution and grading rubric:
Correct. Since the smartphone's upright, enlarged virtual image cannot be projected onto a wall, and in order to produce an "upright" image projected on a wall, the smartphone must instead be:
- turned upside-down; and
- pushed further away from the magnifying glass (such that it is placed just outside the focal point).
Nearly correct, but includes minor math errors. Neglects to mention that the phone must be turned upside-down.
Nearly correct, but approach has conceptual errors, and/or major/compounded math errors.
Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner. May claim that the smartphone already projects an image onto a wall, or that only the magnifying glass to wall distance needs to be changed.
Implementation of ideas, but credit given for effort rather than merit. No clear attempt at applying properties of lenses, thin lens equations, and ray tracings.
Irrelevant discussion/effectively blank.
Sections 30882, 30883
Exam code: finalm4u1
p: 6 students
r: 2 students
t: 4 students
v: 16 students
x: 9 students
y: 2 students
z: 0 student
A sample "p" response (from student 0001):
Another sample "p" response (from student 1614):
A sample "x" response (from student 1959):