(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 $2 \times 10^8$ m/s, calculate the speed of light in: (i) vacuum, (ii) medium 'A'.

(a) The laws of refraction of light are:

(i) The incident ray, the refracted ray, and the normal to the interface at the point of incidence all lie in the same plane.

(ii) The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for a given pair of media.

The absolute refractive index of a medium is the ratio of the speed of light in vacuum to the speed of light in the medium.

(b) (i) Speed of light in vacuum = 2 x 10^8 m/s x 1.5 = 3 x 10^8 m/s

(ii) Speed of light in medium A = 3 x 10^8 m/s / 2.0 = 1.5 x 10^8 m/s