Question

A ray of light in air is incident to an air-to-glass boundary at an angle of exactly 30° with the normal. If the index of refraction of the glass is 1.65, what is the angle of the refracted ray within the glass with respect to the normal?

Answer 1

In order to calculate the angle of the refracted ray, we can use the law of refraction (Snell's Law) below:

$\frac{\sin\theta_1}{\sin\theta_2}=\frac{n_2}{n_1}$

Where n1 and n2 are the indexes of refraction and theta1 and theta2 are the angles of the ray.

So, using n1 = 1, n2 = 1.65 and theta1 = 30°, we have:

$\begin{gathered} \frac{\sin30°}{\sin\theta_2}=\frac{1.65}{1}\\ \\ \frac{\frac{1}{2}}{\sin\theta_2}=1.65\\ \\ \sin\theta_2=\frac{\frac{1}{2}}{1.65}=\frac{1}{3.3}=0.303\\ \\ \theta_2=17.64° \end{gathered}$