Fluorescence
Fluorescence (pronounced: /fluːˈrɛsəns/) is a type of luminescence. It is the emission of light by a substance that has absorbed light or other electromagnetic radiation.
Etymology
The term fluorescence is derived from the mineral fluorite, which will often markedly exhibit this effect. The name was coined by George Gabriel Stokes in 1852.
Principle
When a photon is absorbed by a fluorescent substance, its electrons are excited to a higher energy level. The excited electrons then drop back to a lower energy level, emitting a photon of light in the process. This emitted light has a longer wavelength (and lower energy) than the absorbed radiation.
Applications
Fluorescence has many practical applications, including mineralogy, gemology, chemical sensors (fluorescence spectroscopy), fluorescent labelling, dyes, and biological detectors. In medicine, it is used in some diagnostic procedures, for example, in histology with fluorescent stains, and in fluorescence in situ hybridization, to look at genetic material.
Related Terms
- Phosphorescence: A specific type of photoluminescence related to fluorescence. Unlike fluorescence, a phosphorescent material does not immediately re-emit the radiation it absorbs.
- Fluorophore: A fluorescent chemical compound that can re-emit light upon light excitation.
- Spectroscopy: The study of the interaction between matter and electromagnetic radiation.
External links
- Medical encyclopedia article on Fluorescence
- Wikipedia's article - Fluorescence
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