Question

A ray of light passes from water through a plate of crown glass and on to air. The angle of incidence in the water is 40.0 °.

What then is the angle of refraction in the glass?

Answer 1

We can use Snell's law to calculate the angle of refraction $\theta_2$ in glass. We have two media: water with n₁=1.33 and glass with n₂=1.655. Then

$$\frac{\text{sin}\theta_1}{\text{sin}\theta_2}=\frac{n_2}{n_1},\\ \theta_2=\text{arcsin}\bigg(\text{sin}\theta_1\frac{n_1}{n_2}\bigg)=\\\space\\ \theta_2=\text{arcsin}\bigg(\text{sin}40°\frac{1.33}{1.655}\bigg)=31°.$$