[ ih-rey-dee-uh ns ]
/ ɪˈreɪ di əns /

noun Physics.

incident flux of radiant energy per unit area.

Origin of irradiance

First recorded in 1660–70; ir-1 + radiance Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for irradiance

  • Their irradiance was greenish, like the walls; but I was certain that these corpuscles did not come from them.

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

    Ben Blair|Will Lillibridge

British Dictionary definitions for irradiance


/ (ɪˈreɪdɪəns) /


the radiant flux incident on unit area of a surface. It is measured in watts per square metreSymbol: E e 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