Many common observations are inexplicable by single-scattering arguments: the variation of
brightness and color of the clear sky; the brightness of clouds; the whiteness of a glass of
milk; the appearance of distant objects; the blueness of light transmitted in snow and other
natural ice bodies; the darkening of sand upon wetting. Yet multiple scattering is seldom
mentioned in optics textbooks. It is possible to understand many observable phenomena
without invoking the complete theory of multiple (incoherent) scattering. A simple two-stream …