Albedo
Albedo is the ratio of reflected to incident electromagnetic radiation. It is a unitless measure indicative of a surface's or body's diffuse reflectivity. The word is derived from albus, a Latin word for "white".
Percentage of reflected sun light in relation to various surface conditions of the earth
The albedo is an important concept particularly in
climatology and
astronomy. In climatology it is sometimes expressed as a percentage. Its value depends on the
frequency of radiation considered: unqualified, it usually refers to some appropriate average across the spectrum of
visible light. In general, the albedo depends on the direction and directional distribution of incoming radiation. Exceptions are
Lambertian surfaces, which scatter radiation equally in all directions, so their albedo does not depend on the incoming distribution. In realistic cases, a
bidirectional reflectance distribution function (BRDF) is required to characterise the scattering properties of a surface accurately, although albedos are a very useful first approximation
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