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The Church of St. Eustache, Paris (French: église Saint-Eustache, pronounced [eɡliz sɛ̃t‿østaʃ]), is a church in the 1st arrondissement of Paris. The present ...
Photophores on a lanternfish, the most common deep sea fish worldwide. Counter-illumination relies on organs that produce light, photophores. These are roughly spherical structures that appear as luminous spots on many marine animals, including fish and cephalopods.
Luminescence is a spontaneous emission of radiation from an electronically or vibrationally excited species not in thermal equilibrium with its environment. [ 1 ] A luminescent object emits cold light in contrast to incandescence , where an object only emits light after heating. [ 2 ]
Whereas the term "fluorescence" tended to refer to luminescence that ceased immediately (by human-eye standards) when removed from excitation, "phosphorescence" referred to virtually any substance that glowed for appreciable periods in darkness, sometimes to include even chemiluminescence (which occasionally produced substantial amounts of heat).
A tea light-type candle, imaged with a luminance camera; false colors indicate luminance levels per the bar on the right (cd/m 2). Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. [1]
The amount of luminescence is proportional to the original dose of radiation received. In thermoluminescence dating, this can be used to date buried objects that have been heated in the past, since the ionizing dose received from radioactive elements in the soil or from cosmic rays is proportional to age. This phenomenon has been applied in the ...
Persistent luminescence involves energy traps (such as electron or hole traps) in a material, [4] which are filled during the excitation. Afterward, the stored energy is gradually released to light emitter centers, usually by a fluorescence-like mechanism.
Quantity Unit Dimension [nb 1]Notes Name Symbol [nb 2] Name Symbol Luminous energy: Q v [nb 3]: lumen second: lm⋅s : T⋅J: The lumen second is sometimes called the talbot.: Luminous flux, luminous power