The phenomenon that explains the bending of light is known as refraction. Refraction occurs when light travels from one medium to another and changes its speed, leading to an alteration in direction. This can be observed, for example, when light passes from air into water or glass; the change in density between mediums causes the light rays to bend. The amount of bending depends on the indices of refraction of the two mediums involved and is described by Snell's Law. Refraction is a key principle in optics and is responsible for various optical effects, such as rainbows and the focusing ability of lenses.