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Mass of a Photon

  1. Nov 10, 2015 #1
    If the energy of a photon: Ephoton = hν, where h = Planck's constant,
    and E = mc2, then does hv = mc2

    And if so, if c=vλ: Ephoton = hc/λ = mc2

    Thus mass: m = h/λc ?
  2. jcsd
  3. Nov 10, 2015 #2


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    ##E=mc^2## only applies to massive particles at rest, not photons. You need to use the full equation which is
    ##E^2 = m^2c^4 + p^2 c^2##
  4. Nov 10, 2015 #3
    So what is the momentum of photons since gravitation is applied?
  5. Nov 10, 2015 #4


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    Set m=0 and you get ##E = pc##. You can solve for the momentum of the photon.
  6. Nov 10, 2015 #5
    Ah. Thank you
  7. Nov 10, 2015 #6


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    Staff Emeritus
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    Please note that this has been covered and answered in one of our FAQ.

    Last edited: Nov 10, 2015
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