Question

A ray of light passing FROM water TO air plate at an angle of 30° with the normal. Determine

the

a. angle between the refracted ray and

b. the reflected ray.

(please see the table provided)

(With solution)

Answer 1

First, find the angle of refraction using Snell's law:

$$n_w=\frac{\sin\theta_r}{\sin\theta_i},\\\space\\ \theta_r=\arcsin(n_w\sin\theta_i)=42°.$$

So, the angle between the refracted ray (42° to the normal in air) and the reflected ray (30° to the normal in water) is

$$\alpha=(90°-\theta_r)+(90°-\theta_i)=108°.$$