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Homework Help: Number of photons to make a black hole

  1. Feb 1, 2009 #1
    1. The problem statement, all variables and given/known data

    By setting the total energy of photons to Mc^2, estimate the maximum number of photons that could be used to make a black hole of mass M.

    This is a thermal physics problem, in case anyone needs a context; we're discussing the entropy of a black hole.

    2. Relevant equations

    I'm given the entropy for a black hole. I also know the Schwarzschild radius.

    3. The attempt at a solution

    I'm just having trouble seeing where to start. Probably this is something very basic and I'm just missing it. Can someone just help me to start?
  2. jcsd
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