The angle of refraction for a ray of light passing through the interface between two mediums is given by:

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

Where:

• $n_1$: Index of refraction of incident medium.
• $\theta_1$[°]: Incident ray angle.
• $n_2$: Index of refraction of exit medium.
• $\theta_2$ [°]: Refracted ray angle.

Assumptions:

• Mediums are non-dispersive.

• Derivation

Snell's law - Wikipedia