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Radiance and Irradiance.

  1. Dec 22, 2009 #1
    Hey, I'm having trouble working out what Radiance and Irradiance are, all the definitions I get are along the lines of something really technical like:

    "For a point of radiant energy, Radiant Intensity, in a specified direction, per unit projected area: Le=(dIe/dA)*Cos(theta) where A is the area and theta is the angle between the specified direction and the surface".

    Would you be kind enough to give me a very simple wordy definition of what these are and the difference between the two? Thank you SO much.
  2. jcsd
  3. Dec 22, 2009 #2


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    Radiance is the power from the source per area into a certain solid angle.
    Irradiance is the power onto a surface per area

    (hint, Irriadiance = I = input )
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