SAT Subject Physics Practice Question 364: Answer and Explanation
60. A laser beam passes from the air into a piece of plexiglass. All of the following are false EXCEPT
A. the velocity decreases.
B. the wavelength increases.
C. the frequency decreases.
D. the period decreases.
E. None of the above is true.
Correct Answer: A
The correct answer is (A). Light slows down in an optically more dense material. Additionally, the wavelength shortens. The frequency remains the same. Since the frequency remains unchanged, the period also remains the same.