SAT Subject Physics Practice Question 588: Answer and Explanation
14. Consider a light wave that passes from air into a very thick clear glass block that has its opposite internal side mirrored (facing into the glass). The light ray passes into the glass block at an angle greater than 0° and less than 90°, strikes the mirrored surface and reflects back through the glass into the air.
What happens while the light ray is in the glass block but before it strikes the mirrored surface?
A. The frequency of the waves increases.
B. The frequency of the waves decreases.
C. The wavelength of the waves decreases.
D. The velocity of the waves decreases.
E. The period of the waves increases.
Correct Answer: D
The correct answer is (D). While the light ray is moving through an optically denser material, its velocity decreases.