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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
  • The amount of solar irradiance has not changed at the bottom of the atmosphere.
  • It is called the total solar irradiance and it has not moved upwards in decades and has in fact declined slightly.
  • The power of heat input during the day depends on local albedo and the sine of the angle of the incident solar irradiance.
  • Beam irradiance, and not merely total power, is everything.
  • Color is simpy the product of the spectral irradiance of the object and the spectral sensitivity of our eye.
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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