Absorption

Absorption, in physics, the taking up of light, heat, or other radiant energy by molecules. The absorbed radiation is converted into heat; the radiation that is not absorbed is reflected. For example, sunlight striking an object will usually have some of its wavelengths absorbed and other wavelengths reflected. If the object looks white, it is because all or nearly all of the radiation is reflected. If the object appears to have any colour other than white, however, it means that some of the visible radiation has been absorbed while other wavelengths have been reflected, causing the sensation of colour when they strike the eye. An object that absorbs all the radiation striking it is known as a blackbody.

Absorption in chemistry is the taking up of one substance by another. For example, a gas such as oxygen may be absorbed, or dissolved, in water.

Adsorption, which is often confused with absorption, refers to the adhesion of molecules of gases and liquids to the surfaces of porous solids. Adsorption is a surface phenomenon; absorption is an intermingling or interpenetration of two substances.