What is Absorption?
absorption. (a) White light is a combination (blending) of those hues of the spectrum which are seen in the rainbow. The hue of a gemstone is due to the absorption of certain portions of white light in its passage through the gemstone. The remainder of the light which is not absorbed in the gemstone combines or blends to produce the hue seen. This process is called selective absorption. See also selective reflection.
(b) The exact portions of white light which are absorbed by a gemstone or other substance may be determined by means of the spectroscope forming a band of colors known as an absorption spectrum.
(c) Dark zones crossing the spectrum represent the portions of the light absorbed and are known as absorption bands or absorption lines.