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.

Light changes speed as it passes from one medium to another. This is called refraction. The frequency of light does not change as it refracts. The refractive index of a material is a measure of ...

Scientists have long sought to control light in ways that appear to defy the laws of Nature. Negative refraction - a phenomenon where light bends in the opposite direction to its usual behaviour ...