refracted

Refracted is the past participle of refract, and in common usage describes a wave that has changed direction as it passes from one medium to another. Refraction occurs whenever the speed of a wave varies between media. For light, the part of the wave entering a different medium slows or speeds up, causing the wavefronts to tilt and the ray to bend at the boundary.

The bending follows Snell's law: n1 sin θ1 = n2 sin θ2, where n1 and n2 are the refractive indices of the two media and θ1 and θ2 are the angles between the incident and refracted rays and the normal to the interface. The refractive index n is defined as n = c/v, where v is the phase velocity in the medium.

Refracted light can be toward or away from the normal depending on whether the second medium has higher or lower light speed. Example: air to water bends toward the normal; water to air bends away. Refraction is distinct from reflection, though both can occur at a boundary.

Because refractive index varies with wavelength, different colors bend by different amounts, producing dispersion, as seen in prisms and rainbows.

Applications of refraction include lenses in eyeglasses and cameras, fiber-optic communication, and various imaging and measurement devices, as well as the analysis of atmospheric and oceanic phenomena.