Attenuation of the radiant flux when light is passed through a clear medium.
If light of suitable wavelength is passed through a sample, part of the energy is transmitted to the molecules. As a result, the emergent beam Fex has less energy than the incident beam Fin.
The amount of light absorbed generally follows the Lambert-Beer Law and is therefore proportional to the number of absorbing molecules and the path length traversed (d). Absorption spectroscopy; Extinction.
If the medium contains turbidity matter, additional attentuation is caused as a result of light scattering. Scattered light.