It occurs as a result of the emission of a photon by an atom of the substance when it decays from an excited state to its ground state. Fluorescent dyes in washing powders make clothes look brighter.
Luminous paint is phosphorescent.
Other examples of luminescence include triboluminescence , caused by friction, and chemiluminescence , caused by chemical reaction. Bioluminescence , which is seen in glow worms, seaweeds, and other organisms, is a form of chemiluminescence. Radioluminescence is caused by radioactive decay. The Macmillan Encyclopedia 2001 2. bioluminescence A Dictionary of Science, Oxford University Press 3. The Macmillan Encyclopedia 2001 5.