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Homework Help: Solar luminosity

  1. Oct 6, 2009 #1
    1. The problem statement, all variables and given/known data
    The formula for the surface area of a sphere is 4(3.14) r2, where r is the mean distance from the sun to the earth. Determine the sphere of light (square meters) illuminated by the sun the size of the earth's orbit.

    2. Relevant equations

    astronomical Unit-149,597,829 k

    3. The attempt at a solution
    my answer is 2.8122922(17)
    no idea
    Last edited: Oct 6, 2009
  2. jcsd
  3. Oct 6, 2009 #2


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    Homework Helper

    Welcome to the Physics Forum, newsflash!

    S = 4(3.14) r^2
    = 4*3.14*(149,597,829 km)^2
    = 2.81 x 10^15 km^2
    If you need that in square meters, I suggest you change the r value into meters before squaring. It is tricky changing units on something after it is squared.
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