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Why are electromagnetic waves transverse waves? Is this answer ok?

  1. Sep 10, 2011 #1
    From: http://answers.yahoo.com/question/index?qid=20090223155307AAgqbWk

    Question: Why are electromagnetic waves transverse waves?

    Answer: "Because they are generated by the rapid vibration of elecrons, which go side to side, perpendicular to the direction the waves travel (very very rapid vibration, mind you)"

    How might you improve this answer?

    Thanks for any help!
  2. jcsd
  3. Sep 10, 2011 #2


    Staff: Mentor

    EM waves are transverse waves because they can be polarized.
  4. Sep 10, 2011 #3
    You can use Maxwell's equations to show that a plane wave in free space is transverse. Imagine a plane wave travelling in the x direction, E(x,t).

    Gauss' law states [itex]\frac{\partial E_{x}}{\partial x}=0[/itex] since there is no field variation in the y,z directions.
    Ampere's law states [itex]\mu_{0}\epsilon_{0}\frac{\partial E_x}{\partial t}=\frac{\partial B_z}{\partial y}-\frac{\partial B_y}{\partial z}=0[/itex] for the same reason.

    So the component of E in the direction of propagation does not vary in space or time, ie the wave is transverse.

    Since you can represent a solution to the wave equation by a sum of plane waves, this is enough to show that EM waves are transverse in isotropic, homogeneous media.
  5. Sep 10, 2011 #4
    Hi, Spinnor

    We observe transverse components as electromagnetic waves.
    Longitudinal component is observed as static field.

    I am not so confident in my answer. Correction from you is fully appreciated.

    Last edited: Sep 10, 2011
  6. Sep 10, 2011 #5
    Back in the days when scientists believed in a frictionless aether fluid in order to explain propagation of light through space, one of the arguments against the existence of aether was the fact that transverse waves can only be propagated though a solid medium.
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