Question

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

Answer 1

The correct option is: (C) 1.33 v 

Explanation:

From n = c/v.

n₁ = c/v₁ … 1.5 = c / v_X … v_X = c / 1.5

n2 = c/v2 … 2.0 = c / v_Y … v_Y = c/2

The problem defines v_Y = v

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