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In optics, Lambert's cosine law says that the observed radiant intensity or luminous intensity from an ideal diffusely reflecting surface or ideal diffuse radiator is directly proportional to the cosine of the angle θ between the observer's line of sight and the surface normal; I = I 0 cos θ.
Diagram of Lambertian diffuse reflection. The black arrow shows incident radiance, and the red arrows show the reflected radiant intensity in each direction. When viewed from various angles, the reflected radiant intensity and the apparent area of the surface both vary with the cosine of the viewing angle, so the reflected radiance (intensity per unit area) is the same from all viewing angles.
The rays represent luminous intensity, which varies according to Lambert's cosine law for an ideal diffuse reflector. Diffuse reflection is the reflection of light or other waves or particles from a surface such that a ray incident on the surface is scattered at many angles rather than at just one angle as in the case of specular reflection.
English: A diagram showing a cross section of the radiaton from Lambertian surface - that is, directly propertional to the cosine of the angle between the observer's line of sight and the surface normal.
English: A diagram showing observed intensity (from a Lambertian surface; units: photons/(s·cm 2 ·sr)) for a normal and off-normal observer; dA 0 is the area of the observing aperture and dΩ is the solid angle subtended by the aperture from the viewpoint of the emitting area element.
Radiant intensity is used to characterize the emission of radiation by an antenna: [2], = (), where E e is the irradiance of the antenna;; r is the distance from the antenna.; Unlike power density, radiant intensity does not depend on distance: because radiant intensity is defined as the power through a solid angle, the decreasing power density over distance due to the inverse-square law is ...
Lambert's cosine law: Physics: Johann Heinrich Lambert: Lamm equation: Chemistry, Biophysics: Ole Lamm: Langmuir equation: Surface Chemistry: Irving Langmuir: Laplace transform Laplace's equation Laplace operator Laplace distribution Laplace invariant Laplace expansion Laplace principle Laplace limit See also: List of things named after Pierre ...
Lambert began conducting photometric experiments in 1755 and by August 1757 had enough material to begin writing. [11] From the references in Photometria and the catalogue of his library auctioned after his death, it is clear that Lambert consulted the optical works of Isaac Newton, Pierre Bouguer, Leonhard Euler, Christiaan Huygens, Robert Smith, and Abraham Gotthelf Kästner. [12]