Refraction occurs when light bends as it passes through a distorting material from one material to another.

Definition of Light

Light waves are a type of electromagnetic wave. Electromagnetic waves are different than waves on a string or sound waves in that they don't need anything to travel through. They're just waves of pure energy and because of this, they can travel through a lot of different materials, including empty space. They also move really fast, traveling through space at the speed of light (almost 300 million meters per second!). Although light waves can easily pass through materials like glass, water, and plastic, the waves slow down as they travel through these materials. When the light waves slow down as they pass from one material to another, that's when they're going through refraction.

When the light passes from air into a material like glass or water, it slows down and always bends toward a line drawn a perpendicular to the surface of the material. This line is known as a normal line. When light passes from air into water or glass, it bends towards this normal line.