Question

refractive indices of Glass and water are 3 / 2 and 4 / 3 respectively what is the critical angle between them?

Answer 1

Here, Glass is the denser medium : n1 = 3/2
Water is rarer medium : n2 = 4/3

Light travels from denser to rarer medium.

Let Ø be the critical angle.

Now,

sinØ = 3/2 / 4/3
sinØ = 3/2 * 3/4
SinØ = 9/8
Ø = sin^-1 { 9/8 }

Answer 2

62 deg 43 min

Explanation:

using snell's law n1 sin i = n2 sin r
here sin r = 1 (since r=90 deg)
n1 =3/2 and n2=4/3
hence sin i =8/9
sin i = 0.88
hence i = sin^-1 0.88 = 62 deg 43 min