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Is a photon's momentum transverse?

  1. Aug 5, 2009 #1


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    Gold Member

    I understand that light propagates as a transverse wave -- does this mean that the momentum carried by a photon is perpendicular to its path?

    Thanks for the help.
  2. jcsd
  3. Aug 5, 2009 #2

    Doc Al

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    Staff: Mentor

    No. The momentum of a photon (and of an electromagnetic wave) is in the direction of motion.

    (Don't think of the photon as wiggling transversely as it travels; keep the classical electromagnetic wave picture and the photon picture separate.)
  4. Aug 5, 2009 #3
    As Doc Al states, the momentum of a photon is only in the direction of motion. If the photon strikes an electron and produces a photo electron (photoelectric effect). The transverse momentum of the electron (relative to the incoming photon direction) has to be balanced by the transverse momentum of the recoiling atom or lattice.
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