SAT Subject Physics Practice Question 122: Answer and Explanation

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Question: 122

5. A beam of light traveling in medium 1 strikes the interface to another transparent medium, medium 2. If the speed of light is less in medium 2 than in medium 1, the beam will

A. refract toward the normal
B. refract away from the normal
C. undergo total internal reflection
D. have an angle of reflection smaller than the angle of incidence
E. have an angle of reflection greater than the angle of incidence

Correct Answer: A

Explanation:

If the speed of light is less in medium 2 than in medium 1, then medium 2 must have the higher index of refraction; that is, n2 > n1. Snell’s law then implies that θ2 < θ1: The beam will refract toward the normal upon transmission into medium 2.

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