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Homework Help: Basic Optics Question. (wave front)

  1. Apr 23, 2007 #1
    1. The problem statement, all variables and given/known data
    E=Emax.sin(ωt-kx) describes the electric field of a monochromatic plane wave travelling in the x-direction. Verify that a plane which is perpendicular to the x-diretion and moves along the x-axis at the same speed as the wave is a wave front.

    2. Relevant equations

    3. The attempt at a solution
    A "wave front" is a surface where the phase is always the same.

    -----|-------------------|----------> x-axis

    At x1, t2 and x2, t2 must have the same phase which is in the brackets of sin() in "relevant equations".

    ωt1-kx1 = ωt1-kx2

    and I'm guessing since the speed is the same at both points x1/t1 is equal to x2/t2 and we substitute those in or something?? I dunno I've thought about this alot and I'm very stuck!!!!
  2. jcsd
  3. Apr 25, 2007 #2


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    Gold Member

    Here's a hint : the velocity of the wave described is [tex]\frac{\omega}{k}[/tex]
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