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I How can a Photon apparently transfer Momentum without any Mass?

  1. Aug 4, 2017 #1
    Due to Compton - Scattering it seems that a Photon changes the Momentum of the electron, although it doesn't have any mass. How should I imagine this?
  2. jcsd
  3. Aug 4, 2017 #2


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    A photon is massless but has energy and momentum. It's the mode of an electrodmagnetic field, and you have
    where ##\vec{q}## is the momentum of the photon.

    In relativistic physics you don't need a mass to have a momentum!
  4. Aug 4, 2017 #3


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    Relativistically, the general relationship between energy, momentum, and mass is ##E^2 = (pc)^2 + (mc^2)^2## where p is the magnitude of the momentum. For a photon, m = 0 which gives vanhees71's formula, in different notation.
  5. Aug 4, 2017 #4


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    Staff: Mentor

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