en>Headbomb: Various citation cleanup and WP:AWB general fixes using AWB

2011-09-17T03:01:21Z

Various citation cleanup and WP:AWB general fixes using AWB

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The '''Draper point''' is the approximate temperature above which almost all solid materials visibly glow as a result of [[blackbody]] radiation. It was established at 798 K (525˚ C, 977˚ F) by [[John William Draper]] in 1847.<ref>{{cite journal
| journal = The Academy
| title = Science: Draper's Memoirs
| volume = XIV
| issue = 338
| author =
| publisher = London: Robert Scott Walker
| date = Oct. 26, 1878
| page = 408
| url = http://books.google.com/books?id=hZINAAAAQAAJ&pg=PA408&dq=draper+point+red+1847&lr=&as_brr=0&ei=6sxtSpnpLoLglATlh4RW
}}</ref><ref>{{cite book
| title = Radiation heat transfer: a statistical approach
| author = J. R. Mahan
| edition = 3rd
| publisher = Wiley-IEEE
| year = 2002
| isbn = 978-0-471-21270-6
| page = 58
| url = http://books.google.com/books?id=y9zUEzA7iN0C&pg=PA58&dq=draper-point+red&lr=&as_drrb_is=q&as_minm_is=0&as_miny_is=&as_maxm_is=0&as_maxy_is=&as_brr=3&ei=H8ttSo_2LImMkQTwvuxO
}}</ref><ref>{{cite journal
| title = Production of Light by Heat
| author = John William Draper
| journal = The London, Edinburgh and Dublin philosophical magazine and journal of science
| publisher = Taylor & Francis
| year = 1847
| page = 345–359
| url = http://books.google.com/books?id=VEgEAAAAYAAJ&pg=PA345
}}</ref>

Bodies at temperatures just below the Draper point radiate primarily in the [[infrared]] band and at longer wavelengths, and emit negligible visible light. The value of the Draper point can be calculated using [[Wien's displacement law]]: the peak [[frequency]] <math>\nu_{peak}</math> (in [[hertz]]) emitted by a blackbody relates to temperature as follows:<ref>{{cite book |title= Statistical Physics|last= Wannier|first= Gregory H|authorlink= Gregory Wannier|year= 1987|origyear= 1966|publisher= [[Dover Publications]]|location= [[New York City|New York]]|isbn= 978-0-486-65401-0|oclc= 15520414|chapter= Chapter 10-2}}</ref>

:<math>\nu_{peak} = { 2.821 \over h} kT </math>

where

:''k'' is [[Boltzmann's constant]].
:''h'' is [[Planck's constant]].
:''T'' is temperature (in [[kelvin]]s).

Substituting the Draper point into this equation produces a frequency of 46.9 [[hertz|terahertz]]—which is [[infrared]], and largely invisible except for a dull red, at a small fraction of the peak intensity, that is visible to the human eye.<ref>{{cite book | title = Biology: Concepts and Applications | author = Cecie Starr | publisher = Thomson Brooks/Cole | year = 2005 | isbn = 0-534-46226-X | url = http://books.google.com/books?id=RtSpGV_Pl_0C&pg=PA94}}</ref>

== References ==
{{reflist}}


[[Category:Heat transfer]]
[[Category:Thermodynamics]]
[[Category:Electromagnetic radiation]]

Bessel potential - Revision history

en>Headbomb: Various citation cleanup and WP:AWB general fixes using AWB