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Homework Help: Energy and Momentum in Electromagnetic waves

  1. Apr 28, 2004 #1
    Help me...

    A sinusoidal electromagnetic wave from a radio station passes perpendicularly through an open window that has area of .5m^2. At the window, the electic field of the wave has rms value of .02 V/m. How much energy does this wave carry through the window during a 30sec commercial?
  2. jcsd
  3. Apr 28, 2004 #2

    Doc Al

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    Staff: Mentor

    Poynting vector describes energy flow

    The rate of energy flow per unit area of an electromagnetic wave is given by the Poynting vector:
    [tex]\vec{S} = \frac{1}{\mu_0} \vec{E} \times \vec{B}[/tex]

    The magnitude of the Poynting vector can be shown to be:
    [tex]S = \frac{E^2}{c\mu_0}[/tex]
  4. May 3, 2004 #3
    thanks for the reply but i found the answer
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