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[ih-rey-dee-uh ns] /ɪˈreɪ di əns/
noun, Physics.
incident flux of radiant energy per unit area.
Also, irradiation.
Origin of irradiance
1660-70; ir-1 + radiance Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the Web for irradiance
Historical Examples
  • Their irradiance was greenish, like the walls; but I was certain that these corpuscles did not come from them.

    The Metal Monster A. Merritt
  • The irradiance, almost as strong as daylight, but radically different, softened all surrounding objects.

    Ben Blair Will Lillibridge
British Dictionary definitions for irradiance


the radiant flux incident on unit area of a surface. It is measured in watts per square metre Ee Also called irradiation Compare illuminance
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for irradiance

1660s, from irradiant (1520s), from Latin irradiantem (nominative irradians), present participle of irradiare (see irradiate). Related: Irradiancy (1640s).

Online Etymology Dictionary, © 2010 Douglas Harper
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