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Light intensity vs Irradiance

  1. Dec 28, 2008 #1
    What is the relationship between light intensity and irradiance? How do I convert one to the other?
     
  2. jcsd
  3. Dec 28, 2008 #2

    mgb_phys

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    Strictly speaking irradiance is power/area and intensity is power/solid angle.
    Typically irradiance is at the target and intensity is from the source.
    But intensity is often used when you should use irradiance - so often they are the same thing,
     
  4. Dec 28, 2008 #3
    Thanks!
    Isn't W(m^-2) the unit for light intensity?
    So, if I have, let's say, 1W(m^-2)(nm^-1) spectral irradiance, in the 400nm wavelength range, can I say that I have 1x(10^-9)W(m^-2) light intensity over the same area?
     
  5. Dec 28, 2008 #4

    mgb_phys

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    Nope that the unit of irradiance. As I said - intensity is often losely used when you should say irradiance.

    It depends on the bandwidth, if you have 1W(m^-2)(nm^-1) then you would have 100W/m^2 over a 100nm bandwidth
     
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