Question

(a) (i) Define refractive index of a medium in terms of velocity of light. 

(ii) A ray of light moves from a rare medium to a dense medium as shown in the diagram below. Write down the number of the ray which represents the partially reflected ray. 

(b) You are provided with a printed piece of paper. Using this paper how will you differentiate between a convex lens and a concave lens? 

(c) A ray of light incident at an angle of incidence ‘V passes through an equilateral glass prism such that the refracted ray inside the prism is parallel to its base and emerges from the prism at an angle of emergence ‘e’ 

(i) How is the angle of emergence ‘e’ related to the angle of incidence ‘i’? 

(ii) What can you say about the value of the angle of deviation in such a situation?

Answer 1

(a) (i) Refractive index of a medium is the ratio of velocity of light in vacuum or air to the velocity of light in a given medium.

R.I. = ^airμ_medium 

(ii) Ray 2, represents partially reflected ray. 

(b) Hold each of the lens 5cm above the printed paper and look for the image. In case of convex lens the print appears enlarged. However, in case of concave lens, the print appears diminished. 

(c) (i) Angle of incidence is equal to the angle of emergence 

(ii) The angle of deviation is minimum in this particular case.