Question

In an experiment to determine the refractive index of glass of a prism; the (i) vs. (δ ) graph is plotted. It was found that a ray incident, at an angle of 35° , suffers a deviation of 40° and it emerges at an angle of 79° . Which is the closest possible value of μ ?

(1) 1.5

(2) 1.6

(3) 1.7

(4) 1.8

Answer 1

(1) 1.5

For a prism of refracting angle A; a ray incident at an angle i₁ ; emerges out at angle i₂ . The deviation, δ , is

The refractive index μ of prism is given by

Assuming that incident ray has undergone minimum deviation we have

The deviation, for the given incident ray, may not be the minimum value of deviation. We can, therefore, only say that μ is close to 1.5.