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What do Electromagnetic waves actually look like in space?

  1. Aug 23, 2012 #1
    I know they're represented as sine waves but what would they actually look like in space. they wouldnt actually physically go up and down and side to side like a sine wave would they? I have seen representations of sound waves, which i assume is a longitudinal wave, but not a EM wave.
  2. jcsd
  3. Aug 23, 2012 #2
    Well they don't really have a specific shape because they oscillate in time. But a single wavefront is just a spherical pulse that radiates outward, and at large distance from the source can be approximated as a plane wave.
  4. Aug 23, 2012 #3
    What do you mean they oscillate in time? and do these spherical pulses propagate in a spherical direction from the source?
  5. Aug 24, 2012 #4

    Claude Bile

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    Correct, the sinusoidal component of an EM represents the strength and polarisation of the EM field, not physical displacement as in the case of an acoustic wave.

  6. Aug 24, 2012 #5


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    The 'wiggly line' you see in representations of EM waves is not a picture of how something 'looks'. It's just a graphical representation of the amplitude and direction (vector) of the Electric and Magnetic Fields.
    A similar thing can be done when plotting sound waves - which are longitudinal, of course. You can represent the instantaneous pressure at a point in space on an axis at right angles to the movement and this will also look like a wiggly line. It is not a picture of what happens but it is is a lot better way of showing what goes on than trying to draw dots and lines of different spacing, which is very difficult to do, for a start!
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