Diffusion

Reflection [The following is from Rainwater/'Light and Color']
Reflection. It is of two kinds--diffuse and regular. Diffuse reflection is the kind by which we ordinarily see objects. It gives us information about their shape, size, color and texture. Regular reflection is mirrorlike. We don't see the surface of the mirror; instead, we see objects that are reflected in it. When light strikes a mirror at an angle, it is reflected at the same angle. In diffuse reflection, light leaves at many different angels. The degree of surface roughness determines the proportion of diffuse and regular reflection that occurs. Reflection from a smooth, polished surface like a mirror is mostly regular, while diffuse reflection takes place at surfaces that are rough compared with the wavelength of light. Since the wavelength of light is very small (about 5,000 A), most reflection is diffuse . . . . Viewed microscopically, all reflection is regular. The appearance of diffuse reflection is due to the many different angles that light rays encounter when they strike a rough surface. The reflection of each single ray is regular--that is, it is reflected at the same angle at which it strikes the surface. A fairly smooth surface, such as that of a glossy vinyl raincoat, shows both diffuse and regular reflection, the relative proportions depending on the angle of the incident light. But a rough surface, such as that of a tweed coat, shows only diffuse reflection. It has no "shiny" surface. [pg. 39] [Light and Color, by Clarence Rainwater, Prof. of Physics, San Francisco State College, Original Project Editor Herbert S. Zim, Golden Press, NY, Western Publishing Company, Inc., 1971.]

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1 Diffuse adj [ME, fr. L diffusus, pp. of diffundere to spread out, fr. dis- + fundere to pour -more at Found] [15c] 1: being at once verbose and ill-organized 2: not concenrated or localized [__ sclerosis] syn see Wordy

2 Diffuse vb [ME diffused, pp. fr. L diffusus, pp.] vt [14c] 1a: to pour out and permit or cause to spread freely b: Extend, Scatter c: to spread thinly or wastefully 2: to subject to diffusion; esp: to break up and distribute [incident light] by reflection -vi 1: to spread out or become transmitted esp. by contact 2: to undergo diffusion