Reflectivity

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In optics, reflectivity is the reflectance (the ratio of reflected power to incident power, generally expressed in decibels or percentage) at the surface of a material so thick that the reflectance does not change with increasing thickness; i.e., the intrinsic reflectance of the surface, irrespective of other parameters such as the reflectance of the rear surface. The concept is of some importance in telecommunications.

Surface reflectance may be subdivided into diffuse or Lambertian reflectance and specular reflectance. The apparent reflectance for an ideal Lambertian surface is independent of the observer's angle of view. This contrasts with a shiny (specular) surface, where the apparent brightness is highest when the observing angle is equal and opposite to the source angle. Most real objects have some mixture of diffuse and specular qualities.

Source: from Federal Standard 1037C

Note: In climatology, reflectivity is called albedo.it:Riflettanza