Geometric Optics unit test
A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.
Total internal reflection
Converging optics depend on position
Critical angle
Two conditions for total internal reflection
Snell's law direction
Why light bends at all
Two-element sequence
Magnification
Plane mirror image
Index of refraction
Concave mirror
Ray diagram rules for a lens
Short answer 1. Define or explain: Snell's law
3 ptsShort answer 2. Define or explain: Why the image of a half-covered lens is dimmer, not halved
3 ptsShort answer 3. Define or explain: Sign conventions for lenses and mirrors
3 ptsShort answer 4. Define or explain: Wavelength in a medium
3 ptsFree response
8 ptsAn object is placed a distance 3f in front of a thin converging lens of focal length f. The same object is then placed the same distance 3f in front of a second thin converging lens whose focal length is 2f.
A. Indicate whether the image formed by the second lens is larger than, smaller than, or the same size as the image formed by the first lens. Justify your answer using qualitative reasoning beyond referencing equations.
B. Starting from the thin-lens equation, derive expressions for the image distance and the magnification produced by a converging lens of focal length f when the object is at distance 3f.
C. Justify how your derived expressions in part B are or are not consistent with your comparison in part A.