An Etymological Dictionary of Astronomy and Astrophysics
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A centimeter-gram-second (cgs) unit of luminance (or brightness) equal to 1/π candle per square centimeter. Physically, the lambert is the luminance of a perfectly diffusing white surface receiving an illuminance of 1 lumen per square centimeter.

Johann Heinrich Lambert (1728-1777), German scientist and mathematician; → law.

The intensity of the light emanating in any given direction from a perfectly diffusing surface is proportional to the cosine of the angle between the direction and the normal to the surface. Also called → Lambert's law.

→ lambert; → cosine; → law.

Same as → Lambert's cosine law.

→ lambert; → law.

A → planetary or → satellite disk with → Lambertian surface. Such a disk has the same → surface brightness at all angles.

→ lambert; → disk.

A surface whose → luminous intensity obeys → Lambert's cosine law. Such a source has a → reflectance that is uniform across its surface and uniformly emits in all directions from all its points. It appears equally bright from all viewing directions. Lambertian surface is a very useful concept for the approximation of radiant power transfer.

→ lambert; → surface.