Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: 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

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    [tex] I = 4 \pi \sigma T^4 R_{\rm star}^4/ (R_{star} + r)^2 [/tex]
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook