A ray of light incident at an angle of incidence i₁ passes through an equilateral glass prism such that the refracted ray inside the prism is parallel to its base and emerges at an angle of emergence i₂.

(i) How is the angle of emergence 'i₂' related to the angle of incidence 'i₁'.

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

A light ray of yellow colour is incident on an equilateral glass prism at an angle of incidence equal to 48° and suffers minimum deviation by an angle of 36°.

(i) What will be the angle of emergence?

(ii) If the angle of incidence is changed to (a) 30°, (b) 60°, state in each case whether the angle of deviation will be equal to less than or more than 36°?

What is a prism? With the help of a diagram of the principal section of a prism, indicate its refracting surfaces, refracting angle and base.

The diagrams (a) and (b) in figure below show the refraction of a ray of light of single colour through a prism and a parallel sided glass slab, respectively.

(a)

(b)

(i) In each diagram, label the incident, refracted, emergent rays and the angle of deviation.

(ii) In what way the direction of the emergent ray in the two cases differ with respect to the incident ray? Explain your answer.