This occurs because the speed of light varies in different materials, causing the light to bend at the boundary between the two media…

Refraction is the phenomenon where light waves change direction as they pass from one medium to another with a different density.

This occurs because the speed of light varies in different materials, causing the light to bend at the boundary between the two media.

For example, when a light beam travels from air into water, it slows down and bends toward the normal line (an imaginary line perpendicular to the surface of the boundary). This bending effect is responsible for many common optical phenomena, such as the apparent bending of a straw in a glass of water or the focusing of light by lenses in glasses and cameras. Refraction is described by Snell's Law, which relates the angle of incidence to the angle of refraction, taking into account the refractive indices of the two media.