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Thermal radiation

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+#REDIRECT [[Thermal radiation]]
-{{Short description|Emission of electromagnetic radiation from a hot body}}
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-{{redirect|Incandescent|the album by Crumbächer|Incandescent (album)}}
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-{{About||the science fiction novel with the same name|Incandescence (novel)|information on the intensity and spectrum (color) of incandescence|thermal radiation}}
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-[[File:Hot metalwork.jpg|thumb|right|Hot metal work glows with visible light. This [[thermal radiation]] also extends into the [[infrared]], invisible to the human eye and the camera the image was taken with, but an [[infrared camera]] could show it (See [[Thermography]]).]]
-[[File:Incandescence.jpg|thumb|The incandescent metal embers of the [[spark (fire)|spark]] used to light this [[Bunsen burner]] emit light ranging in color from white to orange to yellow to red or to blue. This change correlates with their temperature as they cool in the air. The flame itself is not incandescent, as its [[Swan bands|blue color]] comes from the quantized transitions that result from the oxidation of CH radicals.]]
-'''Incandescence''' is the emission of [[electromagnetic radiation]] (including visible [[light]]) from a hot body as a result of its high temperature.<ref>{{cite book | title = Treatise on Heat | author = Dionysius Lardner | author-link = Dionysius Lardner | publisher = Longman, Rees, Orme, Brown, Green & Longman | year = 1833 | url = https://archive.org/details/treatiseonheat00lardgoog | page = [https://archive.org/details/treatiseonheat00lardgoog/page/n364 341] | quote = The state in which a heated body, naturally incapable of emitting light, becomes [[luminosity|luminous]], is called a state of ''incandescence''. }}</ref>  The term derives from the Latin verb ''incandescere,'' to glow white.<ref>{{cite book | title = An Introduction to Practical Chemistry, Including Analysis | author = John E. Bowman | edition = Second American | publisher = Philadelphia: Blanchard and Lea | year = 1856 | url = https://archive.org/details/anintroductiont01bowmgoog | page = [https://archive.org/details/anintroductiont01bowmgoog/page/n289 283] | quote = incandesce 0-1860. }}</ref> A common use of incandescence is the [[Incandescent light bulb|incandescent light bulb]], now [[Phase-out of incandescent light bulbs|being phased out]].
-Incandescence is due to [[thermal radiation]]. It usually refers specifically to [[visible light]], while thermal radiation refers also to [[infrared]] or any other [[electromagnetic radiation]].
-==Observation and use==
-{{main|Thermal radiation}}
-In practice, virtually all solid or liquid substances start to glow around {{convert|798|K|C F}}, with a mildly dull red color, whether or not a chemical reaction takes place that produces light as a result of an exothermic process. This limit is called the [[Draper point]]. The incandescence does not vanish below that temperature, but it is too weak in the visible spectrum to be perceptible.
-At higher temperatures, the substance becomes brighter and its color changes from red towards white and finally blue.
-Incandescence is exploited in [[incandescent light bulb]]s, in which a filament is heated to a temperature at which a fraction of the radiation falls in the visible spectrum. The majority of the radiation, however, is emitted in the infrared part of the spectrum, rendering incandescent lights relatively inefficient as a light source.<ref>{{cite book | title = Illumination and Photometry | author = William Elgin Wickenden | publisher = McGraw-Hill | year = 1910 | url = https://archive.org/details/illuminationphot00wickrich | page = [https://archive.org/details/illuminationphot00wickrich/page/3 3] | quote = incandescent low-efficiency blackbody. }}</ref> If the filament could be made hotter, efficiency would increase; however, there are currently no materials able to withstand such temperatures which would be appropriate for use in lamps.
-More efficient light sources, such as [[fluorescent lamp]]s and [[LED]]s, do not function by incandescence.<ref>{{Cite book|url=https://books.google.com/books?id=Tdrp2F3BExAC&q=fluorescent+light+and+LEDs%2C+do+not+function+by+incandescence.&pg=PT115|title=Prefabulous + Almost Off the Grid: Your Path to Building an Energy-Independent Home|last=Koones|first=Sheri|date=2012-10-01|publisher=Abrams|isbn=9781613123966|language=en}}</ref>
-[[Sunlight]] is the incandescence of the "white hot" surface of the [[sun]].
-==See also==
-[[File:Example incandescence colors (temperature range 550 - 1300 C).svg|The visible color of an object heated to incandescence (from 550°C to 1300°C (1022°F to 2372°F))|thumb]]
-*[[Red heat]]
-*[[List of light sources]]
-*[[luminescence]] (light emission by substances ''not'' resulting from heat)
-==References==
-{{Reflist}}
-==External links==
-{{Artificial light sources}}
-[[Category:Electromagnetic radiation]]
-[[Category:Light sources]]
-[[Category:Luminescence]]