Hemispheric Quantities Extinction and Emission Radiation and matter have only two forms of interactions, extinction and emission.
Extinction includes all processes which reduce the radiant intensity.
As will be described below, these processes include absorption and scattering which removes photons from the beam. Emission includes all processes which increase the radiant intensity. As will be described below, these processes include thermal emission and scattering which adds photons to the beam. Determination of , which contains all the information about the electromagnetic properties of the media, is the subject of active theoretical, laboratory and field research. Extinction and emission are linear processes, and thus additive.