Lambert's law

noun Optics.
  1. the law that the luminous intensity of a perfectly diffusing surface in any direction is proportional to the cosine of the angle between that direction and the normal to the surface, for which reason the surface will appear equally bright from all directions.

Origin of Lambert's law

after J. H. Lambert
Also called cosine law.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018