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Homework Help: Need help finding energy absorbed by perfect black sphere

  1. Nov 19, 2011 #1
    1. The problem statement, all variables and given/known data
    Suppose we place a perfectly black sphere (i.e., a sphere that absorbs all energy it receives)
    with radius 2500 km at a distance of 5.2 AU from the Sun. How much energy does the sphere
    absorb in one second?
    energy emitted by sun is given to be 3.90 * 10^26

    2. Relevant equations
    flux = energy emitted(luminosity)/Area

    3. The attempt at a solution
    I found the area of the black sphere and the area of the energy emitted.
    But I do not no what the next step should be. would i need to find the flux of the black sphere first then find how much energy it receives.
    I am not looking for a solution to the question but how I would go about trying to solve it.
    Can someone please help.
  2. jcsd
  3. Nov 19, 2011 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    Figure out how much flux the black sphere receives FROM the sun at that distance. Figure out the area over which the radiation is incident. That will tell you the total power absorbed by the sphere.
  4. Nov 20, 2011 #3
    Thank you for the help
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