Luminescence
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Luminescence is light that usually occurs at low temperatures, and is thus a form of cold body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions, or stress on a crystal. This distinguishes luminescence from incandescence, which is light generated by high temperatures. Historically, radioactivity was thought of as a form of "radioluminescence", although it is today considered to be separate since it involves more than electromagnetic radiation.
The dials, hands, scales and signs of aviation and navigational instruments and markings are often coated with luminescent materials, in a process known as luminising.
The following are types of luminescence
- Bioluminescence, by a living organism
- Chemoluminescence, resulting of a chemical reaction
- Crystalloluminescence, produced during crystallization
- Electroluminescence, in response to an electric current passed through it
- Cathodoluminescence, where beam of electrons impacts on a luminescent material such as a phosphor
- Mechanoluminescence, resulting from any mechanical action on a solid
- Triboluminescence, generated when bonds in a material are broken when that material is scratched, crushed, or rubbed
- Fractoluminescence, generated when bonds in certain crystals are broken by fractures
- Piezoluminescence, produced by the action of pressure on certain solids[1]
- Photoluminescence, absorption of photons causing re-radiation of photons
- Phosphorescence, delayed re-radiation
- Fluorescence, where the emitted photons are of lower energy than those absorbed
- Radioluminescence, produced in a material by the bombardment of ionizing radiation
- Sonoluminescence, from imploding bubbles in a liquid when excited by sound
- Thermoluminescence, when absorbed light is re-emitted on heating.
