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Homework Help: Intensity of light

  1. Jan 10, 2008 #1
    1. The problem statement, all variables and given/known data

    Two identical stars have intensity readings in a 40 to 1 ratio. Calculate the ratio of their distances.

    Two similar lights are at distances in a ratio of 8 to 785. Calculate the ratio of intensities.


    All I want to know is if I use E1D1^2=E2D2^2 or I1/D1^2=I2/D2^2. I'm quite sure I use E1D1^2=E2D2^2 for both. For the first one because they stars are the exact same, and for the second one because they are similar?
     
  2. jcsd
  3. Jan 10, 2008 #2

    olgranpappy

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    Homework Helper

    you'll have to tell us what E, D, and I are.
     
  4. Jan 10, 2008 #3
    E= illumination
    D=distance
    I=intensity
     
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