A relationship describing the rate of decrease of flux density of a plane-parallel beam of monochromatic radiation as it penetrates a medium which both scatters and absorbs at that wavelength. This law may be expressed
alt="alpha sub lambda" height=15 src="equat/alfsbla.gif" width=17 is the attenuation coefficient (or extinction coefficient) of the medium at wavelength Missing Image:IMG alt=lambda height=16 src="equat/lambdasm.gif" width=13; Missing Image:IMG alt="I sub lambda 0" height=19 src="equat/41ilam0.gif" width=24 is the flux density at the source; and x is the distance from the source. Sometimes called Beer law, Lambert law of absorption . See absorption coefficient, scattering coefficient.
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use