SAT Subject Physics Practice Question 651: Answer and Explanation
2. The critical angle for a beam of light passing from a diamond into the air is 24.4°. This means that any light rays that strike the surface interface between the diamond and the air with an angle less than 24.4° are
A. completely reflected.
B. partially reflected and partially refracted.
C. completely absorbed.
D. partially absorbed and partially transmitted.
E. completely transmitted.
Correct Answer: A
The correct answer is (A). Light rays leaving an optically more dense material and striking the surface interface between the two substances are totally reflected back into the material when the angle of incidence is equal to or less than the critical angle.