Question

A ray of light is incident on a glass slab. Which is greater the angle of incidence or the angle of refraction.

1. When the ray travels from air to glass?
2. When the ray travels from glass to air?
3. State two laws of refraction of light.

Answer 1

(a) The angle of incidence is greater than the angle of refraction (i > r), because the ray bends towards the normal as it enters the optically denser glass.

(b) The angle of refraction is greater than the angle of incidence (r > i), because the ray bends away from the normal as it enters the optically rarer air.

(c) The two laws of refraction are:

1. For a given pair of media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant: `sin i/sin r` = constant. This is Snell’s law.
2. The incident ray, the refracted ray and the normal at the point of incidence all lie in the same plane.