How is light absorbed?

Light can be absorbed by materials according to a number of mechanisms that include atomic vibrations and rotations, ligand-field effects, molecular orbitals, and charge transfer. It is very often the case that specific quantities of light (energy) are absorbed by a specific material and thus the light absorbtion properties of materials are usually wavelength selective.

The energy that is absorbed by molecules can be dissipated as kinetic and heat energy, but sometimes the energy can be re-emitted. Fluourescence and phosphorescence are phenomena that result from the re-emission of absorbed light energy: in both cases the re-emitted energy is at a longer wavelength than the light originally absorbed.