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Homework Help: Radiation, temperature of earth, heat transfer

  1. Nov 26, 2011 #1
    If an area of 1 m2 at the earth surface emits Q/t = 54E-3 J/s in radiation, what would the temperature at the earth surface be, if there would be no other energy sources? Assume that the earth is a perfect black body emitter (e = 1).

    Q/t = e(5.67E-8)(A)T4
    54E-3 = 1(5.67E-8)T4
    T = 31.2 K?

    The answer is supposed to be 2.4 K? I feel pretty confident in my work so I am not certain where I have gone wrong.
    Last edited: Nov 26, 2011
  2. jcsd
  3. Nov 27, 2011 #2
    Are you sure your Q/t is correct? The surface of the earth is really -271 C?
  4. Nov 27, 2011 #3


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    Given the numbers given in the problem statement, I agree with the 31.2 K value. It does sound silly to say this takes place somewhere on the Earth's surface though.
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