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Fluorescence

Applications

The most well-known application of fluorescence is the fluorescent lamp, which consists of a glass tube filled with a gas and lined with a fluorescent material. Electricity is made to flow through the gas, causing it to radiate. Often mercury vapor, which radiates in the violet and ultraviolet, is used. This radiation strikes the coating, causing it to fluoresce visible light. Because the fluorescence process is used, the fluorescent lamp is more efficient and generates less heat than an incandescent bulb.

Resonance fluorescence can be used as a laboratory technique for analyzing different phenomena such as the gas flow in a wind tunnel. Art forgeries can be detected by observing the fluorescence of a painting illuminated with ultraviolet light. Painting medium will fluoresce when first applied, then diminish as time passes. In this way paintings that are apparently old, but are really recent forgeries, can be discovered.

John Appel

KEY TERMS

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Angstrom: —A unit of length equal to one ten-billionth of a meter.
Energy level: —The internal energy state of an atom or molecule which is characterized by having only discrete, discontinuous values.
Excited state: —Any energy level with an energy greater than that of the ground state.
Fluorescent efficiency: —The ratio of the intensity of the fluorescent radiation to the intensity of the absorbed radiation.
Fluorescent lamp: —A device that utilizes the phenomenon of fluorescence to produce light for illumination.
Ground state: —The lowest energy level of an atom or molecule.
Metastable state: —An energy level in which an atom or molecule can remain for a period longer than its other energy levels before returning to its ground state.
Phosphorescence: —The persistent emission of radiation by a substance following the removal of the illuminating radiation.
Resonance fluorescence: —Fluorescence in which the emitted radiation has the same wavelength as the absorbed radiation.
Stoke's law: —In fluorescence, the emitted wavelength is always longer than the absorbed wavelength.
Ultraviolet radiation: —Radiation similar to visible light but of shorter wavelength, and thus higher energy.
Visible light: —Electromagnetic radiation of wavelength between 4,000 and 8,000 angstroms.
Wavelength: —The distance between two consecutive crests or troughs in a wave.

Additional topics

Science EncyclopediaScience & Philosophy: Ferroelectric materials to Form and matterFluorescence - Fundamentals, Applications