Question

When light falls on a given plate at angle of incidence of ${60}^o$, the reflected and refracted rays are found to be normal to each other. The refractive index of the material of the plate is then

• A. 0.866
• B. 1.5
• C. 1.732
• D. 2

Answer 1

Answer: (C)

1.732

Given:

Angle of incidence $i={60}^o$.

$i+r={90}^o$

$\therefore r={30}^o$

From Snell's law of refraction we can write,
Now $\mu =\frac{sini}{sinr}=\frac{sin60}{sin30}=\frac{\sqrt{3}/2}{1/2}=\sqrt{3}=1.732$