Question

A ray of light passes through an equilateral prism such that the angle of incidence is equal to the angle of emergence and the latter is equal to 3/4th of the angle of prism. The angle of deviation is(a) 45°(b) 39°(c) 20°(d) 30°

Answer 1

(d)30 degree is the correct answer.

angle of equilateral prism is 60 degree and angle of emergence = 45 degree(3/4th the angle of prism-given in Question).

Angle of emergence = angle of incidence = 45 degree.

angle of deviation = 2i-A where i=angle of incidence and A is the angle of the prism.

angle of deviation= 2(45)-60

                              =90-60

                              = 30 degree