Question

Calculate the speed of light in a medium whose critical angle is 30°.

Answer 1

Refractive index is given by, n = 1/Sin ic , where ic is critical angle = 300
So, n = 2
As, n = c/v , where c - speed of light in vacuum and v is the speed of light in medium.
So,  speed of light in given medium (v)  = c/n = 1.5 X108 m /sec

Answer 2

n = 1/sinC

  = 1/sin30º​

  = 2

Speed of light in medium v = c/n

                                             = (3 x108)/2

                                             = 1.5 x 108m/s

Hence, the speed of light in a medium whose critical angle is 30° is

1.5 x 108m/s