calculate speed of light in a medium whose critical angle is 30 degree.

Refractive index is given by, n = 1/Sin i_c , where i_c 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