The speed of light in material A is 1.4 times as large as it is in material B.What is the ratio of the refractive indices,nA/nB,of these materials?
A)1.4
B)1.2
C)1.0
D)0.80
E)0.71

Question

Quizplus · Accepted Answer

The refractive index is defined as the ratio of the speed of light in vacuum to the speed of light in a given medium. Thus, we have:
nA = c/vA
nB = c/vB
where c is the speed of light in vacuum, vA is the speed of light in material A, and vB is the speed of light in material B. From the given information, we have:
vA = 1.4vB
Substituting this into the expressions for the refractive indices, we get:
nA/nB = (c/vA)/(c/vB) = vB/vA = 1/1.4 = 0.71
Therefore, the ratio of the refractive indices is 0.71, which corresponds to choice (E).

The Speed of Light in Material a Is 1