What is the Index of Refraction of a Diamond on the SAT

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N.B. SAT Subject Test Physics

Question

The speed of light through a particular diamond is 1.24 X 10^8 m/s. What is the index of refraction of the diamond?

(A) 1.24
(B) 1.76
(C) 2.42
(D) 3.72
(E) 4.13

Answer

(C).

The index of refraction compares the speed of light in a vacuum to the speed in the diamond. 

\[ n = \frac{3.0 \ x \ 10^8 \ m/s}{1.24 \ x \ 10^8 \ m/s} = 2.42 \]