absorption coefficient

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun physics A measure of the absorption of electromagnetic radiation as it passes through a specific substance; the fraction of incident radiation absorbed by unit mass or unit thickness; absorptivity.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a measure of the rate of decrease in the intensity of electromagnetic radiation (as light) as it passes through a given substance; the fraction of incident radiant energy absorbed per unit mass or thickness of an absorber