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Homework Help: Direction of Electric Field in an Electromagnetic Wave

  1. Apr 24, 2015 #1
    1. The problem statement, all variables and given/known data

    If the magnetic field of a light wave oscillates parallel to a y axis and is given by ##B_y = B_m\ sin(kz- \omega t)##,

    (a) in what direction does the wave travel and

    (b) parallel to which axis does the associated electric field oscillate?

    2. Relevant equations

    3. The attempt at a solution

    (a) The wave is propagating in the ##+ z##-direction because the form of the argument in the sinusoidal function.

    (b) I'm having problem here.
  2. jcsd
  3. Apr 24, 2015 #2

    Simon Bridge

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    (b) where are you having the problem?
  4. Apr 24, 2015 #3
    I think I figured it out. :D

    If the direction of propagation is given by ##\overrightarrow(E) \times \overrightarrow(B)##, then shouldn't the direction of the electric field be in the ##+ x##-direction.
  5. Apr 24, 2015 #4

    Simon Bridge

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    That's the one - well done.
    Just remember that the E and B fields are perpendicular.

    LaTeX note: use curly brackets to enclose what you operate on, but not needed if there is only on letter following the command.
    Thus \vec E \times \vec B gets you ##\vec E \times \vec B##
  6. Apr 25, 2015 #5
    Thank you! :)
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