Q.The angle of incidence on the surface of a diamond of refractive index 2.4, if the angle between the reflected and refracted rays is 90° is

(a) tan^{-1}(2.4)

(b) sin^{-1}(1/2.4)

(c) tan^{-1} (1/2.4)

(d) cos^{-1} (1/2.4)

Ans: A

Sol: According to question , i+r=90° ….(i)

Applying Snell’s Law

1×sini = 2.4×sinr

sini = 2.4×sin(90-i) = 2.4cosi from(i)

tani = 2.4

i = tan^{−1}(2.4)