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Will two orthogonally polarized light beams interfere?

  1. Apr 9, 2013 #1
    If Beam A (BA) is polarized vertically, and Beam B (BB) is polarized horizontally, can BA and BB still create an interference pattern if put together.

    For example, in Youngs Double Slit experiment, say BA goes through Slit 1, and BB goes through Slit 2: will an interference pattern result?

    Thank you,

  2. jcsd
  3. Apr 9, 2013 #2


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  4. Apr 9, 2013 #3


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    Two fields at right angles to each other (as in the transverse fields of an EM wave) cannot add vectorially to produce zero - so you cannot get a zero of power in any direction. The two waves will, however, superpose (as always) and, if the two beams are phase coherent, there will be a plane of polarisation in which interference can be observed. It may be easier to think in terms of two transmitting dipoles, placed apart and at right angles. You can expect to find cancellations and nulls but also elliptical polarisation in some directions.
    This doesn't conflict with the F-A Laws, which refer to "readily observed" interference and don't exclude the possibility, totally. I have a feeling that Fresnel did not have radio transmissions in mind when he drew up the laws. Mundane old CW, RF signals may not be as sexy as photons from lasers but they really can help in making good predictions about the way waves are likely to behave.
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