The ratio of the reflected flux to the incident flux, or the ratio of reflected light to light falling on the object.

The return of radiant energy (incident light) by a surface, with no change in wavelength.

The change of direction of propagation of any wave, such as an electromagnetic wave, when it passes from one medium to another in which the wave velocity is different. Simply put, the bending of incident rays as they pass from one medium to another, such as air to water.