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irradiance vs. radiance

[ih-rey-dee-uhns] / ɪˈreɪ di əns /

noun

Physics.
  1. incident flux of radiant energy per unit area.

[rey-dee-uhns] / ˈreɪ di əns /

noun

  1. radiant brightness or light.

    the radiance of the tropical sun.

    Synonyms:
    brilliance, splendor, resplendence
  2. warm, cheerful brightness.

    the radiance of her expression.

  3. Rare. radiation.