Question

List type of Lambert Cosine Law?

Answer 1

In optics, Lambert's cosine law says that the radiant intensity or luminous intensityobserved from an ideal diffusely reflectingsurface or ideal diffuse radiator is directly proportional to the cosine of the angle θbetween the direction of the incident light and the surface normal.[1][2] The law is also known as the cosine emission law[3] or Lambert's emission law. It is named after Johann Heinrich Lambert, from his Photometria, published in 1760.[4]
A surface which obeys Lambert's law is said to be Lambertian, and exhibits Lambertian reflectance. Such a surface has the same radiance when viewed from any angle. This means, for example, that to the human eye it has the same apparent brightness (or luminance). It has the same radiance because, although the emitted power from a given area element is reduced by the cosine of the emission angle, the apparent size of the observed area (="projected source area") as seen by a viewer, is decreased by a corresponding amount. Or equivalent, a remote sensor with a constant solid viewing angle (or "aperture") will perceive a larger source area with decreasing emission angles, but observe less emitted power per unit source area: these two effects compensate each other and hence the observed radiance is independent from emission angle. Therefore, its radiance (power per unit solid angle per unit projected source area) is the same.