Question

A ray of light incident parallel to the base PQ of an isosceles right-angled triangular prism PQR suffers two successive total internal reflections at the faces PQ and QR before emerging reversed in direction as shown below.

If the refractive index of the material of the prism is µ, then

(a) µ > √5

(b) √3 < µ < √5

(c) √2 < µ < √3

(d) µ < √2

Answer 1

Answer is : (a) µ > √5

From the geometry of given figure,

We have, for total internal reflections

From Eq. (ii), we have

Common solution of Eqs. (iii) and (iv) is µ > √5.