The reflection of a portion of the light incident on a planar surface (i.e., the interface) between two media having different refractive indexes.The reflected portion of the light remains in the same plane as the incident light and reflects at the same angle to the normal as the incident ray. The polarization is known as parallel. The extent to which the incident is reflected, rather than refracted, depends on the difference in the index of refraction (IOR) of the individual media (e.g., air and glass), the angle of incidence, the light polarization, and the direction in which the light is passing (e.g., from air to glass or from glass to air). See also angle of incidence; Fresnel, Augustin-Jean; Fresnel refraction; IOR; polarization; reflection; and refraction.