What is Refraction, or refraction of light?

Secrets of Refraction: How to Create a Visual Illusion Using Physics.

Refraction, or refraction of light, is the physical process by which light changes direction as it passes from one medium to another.

This phenomenon can be seen through an amazing experiment. Look at a drawing through a glass of water: the girl suddenly turns to the left.

This happens because light traveling through water and glass changes its speed and direction.

Water has a different density than air, which causes light waves to bend.

When light passes through the curved surface of a glass of water, it is refracted twice: first as it enters the glass, then as it leaves it.

These double refractions create a lens effect that flips the image horizontally.