A beam of light is traveling through air (n = 1) when it passes through a transparent glass (n = 1.5) medium. Which of following is true concerning the angles θ and the velocity V?

A. θ_{1} > θ_{2 }and V_{1} > V_{2}

B. θ_{1} > θ_{2} and V_{1} < V_{2}

C. θ_{1} < θ_{2} and V_{1} > V_{2}

D. θ_{1} < θ_{2} and V_{1} < V_{2}

##### Click for Explanation

This question tests the examinees understanding of Snell’s law of refraction, n_{1}(sinθ _{1}) = n_{2}(sinθ _{2}). The index of refraction (n) is the ratio of the speed of light to the speed of light through a specific medium. The* *index of refraction for air is 1, which means V_{1 }is equal to the speed of light (3 x 10^{8} m/s). The refraction index for glass is 1.5, which makes

V_{2 }= 2 x 10^{8} m/s. Therefore, B and D are eliminated.

To compare the angle of incidence (θ _{1}) to the angle of refraction (θ _{2}), use Snell’s law to determine the ratio. Since (sinθ _{1})/(sinθ _{2}) = n_{2}/n_{1}, θ_{1} must be greater than θ_{2}. **Thus, A is the correct answer.**

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