Light travels from material X with an index of refraction of n=1.5 to material Y with an index of refraction of n = 2.0. If the speed of light in material Y is v, what is the speed of light in material X?

A) 0.56 v 

B) 0.75 v 

C) 1.33 v 

D) 1.78 v 

E) 3.0 v

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1 Answers

The correct option is: (C) 1.33 v 

Explanation:

From n = c/v.

n1 = c/v1 … 1.5 = c / vX … vX = c / 1.5

n2 = c/v2 … 2.0 = c / vY … vY = c/2

The problem defines vY = v

So v = c/2, c = 2v … then subbing that into the vx equation we have vX = (2v) / 1.5 = 1.33 v

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