Refraction occurs when a wave changes direction as it changes speed when it passes from one medium to another.

When can refraction happen?

When a wave or light ray moves from one medium to another its speed changes. The direction of the ray may also change. This property of waves is called refraction and commonly occurs with light rays.

Why does refraction occur?

We have learned that refraction occurs as light passes across the boundary between two media. The only time that a wave can be transmitted across a boundary, change its speed, and still not refract is when the light wave approaches the boundary in a direction that is perpendicular to it. ...