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Intensity (very simple question)

  1. Mar 5, 2006 #1
    but somehow my brain is not working...
    how does the intensity of radiation emitted by a star (but really any hot sphere, really) vary with distance from teh star?

    at the surface the intensity is
    [tex] I = 4 \pi \sigma T^4 R_{star}^2 [/tex]

    as we move away
    [tex] I = 4 \pi \sigma T^4 (R_{star} + r)^2 [/tex] where r is the distnace from the star to some point.

    is that how the intensity varies?
    Square of the sitance from teh center of the star?
  2. jcsd
  3. Mar 5, 2006 #2
    I think the equation that you want might be [tex] I = \frac{I_0}{4 \pi r^2} [/tex], but I'm not entirely sure if that is what you are looking for.
  4. Mar 6, 2006 #3

    Meir Achuz

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    [tex] I = 4 \pi \sigma T^4 R_{\rm star}^4/ (R_{star} + r)^2 [/tex]
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