(a) State the laws of refraction of light. Explain the term absolute refractive index of a medium and write an expression to relate it with the speed of light in vacuum.

(b) The absolute refractive indices of two media 'A' and 'B' are 2.0 and 1.5 respectively. If the speed of light in medium 'B' is , calculate the speed of light in:

(i) vacuum,

(ii) medium 'A'.

Laws of refraction states that:

(1) The incident ray, the refracted ray and the normal to the interface of two media at the point of incidence all lie in the same plane.
(2)  For the light of a given color and for given pair of media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant.

This is also known as Snell's Law.

Mathematically it can be written as:

Here,  is the refractive index of medium B with respect to medium A.

Refractive index of a medium with respect to the vacuum is known as the absolute refractive index.

 c is the speed of light in vacuum and c is the speed of light in medium B.

b) Absolute refractive of medium A,  =2   

Absolute refractive index of medium B,   =1.5