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Homework Help: Momentum in a Box of Light

  1. Jun 2, 2016 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations
    <S>=c[itex] \epsilon [/itex]E2/2

    [itex] \Delta P = A \Delta t <S>/c [/itex]

    3. The attempt at a solution
    My question is if we need the "box height"? This is my work which I'm assuming is wrong. :C New canvas.jpg

    If there's another problem like this on here please put a link. I didn't see any, but my search terms may not have been ideal "Pressure of light in a box".
  2. jcsd
  3. Jun 2, 2016 #2


    User Avatar

    Staff: Mentor

    What is the momentum of the light? Why did 1400 W m-2 become 1000 W m-2? You didn't say why reflection doesn't change the answer.
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