Question

The critical angle for total internal reflection for light traveling from a particular type of glass to air is 39.5 ∘

∘

.

Part A

What is the index of refraction of this glass?

Answer 1

From Snell's law

(Sin of incident angle/ sin of refracted angle) =( Refractive index of the 2nd medium / Refractive index of the 1st medium)

But here the second medium is air, so the refractive index of second medium  is 1. Also at critical angle the angle made by refracted ray with the normal is 900. So sin of refracted angle is 1. Now the euation becomes

sin 39.5 = 1/ refractive index of the 1st medium

therefore the refractive index of the first medium = 1 / sin 39.5

refractive index of glass = 1.57