Reflection describes the return of optical radiation when it reaches a boundary between two different media. A basic distinction is drawn between diffuse and specular reflection.
In diffuse reflection, the returning reflection of directional incoming radiation flux is scattered in many directions. This is caused by an uneven, broken, bumpy boundary surface where the coarseness is of the same order of magnitude as the wavelength.
Lambert’s cosine law applies, to a good approximation, to perfectly diffusing surfaces. This law states that the radiant intensity I at the emission angle θ of a perfectly diffusing surface A of radiance L has a magnitude given by I = L · A cos θ. It follows that the radiance of a Lambertian surface is the same in all directions (isotropic). Such a completely matte white material scatters evenly in all directions, reflecting the radiation independently of the angle, and has a reflection factor with the value 1 (100%).
Additional information in our:
 Products section: Optically Diffuse Reflectance Material
Tutorials: click II.5.c. Lambertian Surface
Download:  Diffuse_Reflectors.pdf (341 kB)
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