(a) State the laws of refraction of light. Give an expression to relate the absolute refractive index of a medium with speed of light in vacuum.
(b) The refractive indices of water and glass with respect to air are `4//3 and 3//2` respectively. If the speed of light in glass is `2xx 10^(8) ms^(-1)`, find the speed of light in (i) air, (ii) water.

Explanation

The laws of refraction are as :
(a) The incident ray, the refracted ray and the normal at the point of incidence all lie in the same plane.
(b) The ratio of sine of angle of incidence to the sine of angle of refraction is a constant for a pair of media. This constant is known as refractive index i.e., `mu` sin i /sin r