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Homework Help: Explanation on how to arrive at equation for EM wave?

  1. Aug 20, 2013 #1
    It is known that the electric field component of the EM wave is given by
    [itex]E=E_{0}cos(kx-\omega t)[/itex]

    How do I arrive at such a form?
    It is quite different from the standard sinusoidal equation of [itex]y=Acos(\omega t+\varphi)[/itex]

    Any guidance?
    What does the [itex]kx-\omega t[/itex] describe physically?
  2. jcsd
  3. Aug 20, 2013 #2


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    Your 'standard form' describes a wave that is constant at all values of x and only varies with t. The given form describes a 'travelling wave' that varies not only with time but with space as well. It has a constant shape but moves at velocity ω/k.
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