Regular and Diffuse Reflection

Abstract

If a parallel beam of light is allowed to fall on the smooth surface of a solid material, two limiting cases arise for the reflected portion of the radiation: it is either reflected “specularly” (that is, as from a mirror), or it is reflected in all directions of the hemisphere uniformly. In the first case, the surface is an ideal reflecting (polished) surface, while in the second it is an ideal matte (scattering) surface. These two ideal limiting cases for a surface are never attained in practice. Even on the best mirrors, such as a mercury surface the place where a beam of light impinges (even outside the incident plane) can be seen. It is desirable, however, to consider the behaviour of such ideal surfaces in a theoretical manner, and then to proceed to the behaviour of real surfaces.