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Virtual photon

  1. Jul 23, 2012 #1
    What is the difference between real photons and virtual photons?
  2. jcsd
  3. Jul 23, 2012 #2


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    Real photons satisfy Einstein's energy relation (or: they are on-shell). Virtual photons don't. As a consequence, the first can be directly measured, the second cannot.
  4. Jul 23, 2012 #3
    Virtual photons are the force carriers of e.m. While real photons are little packets of energy... When two electrons repulse each other they do it because of the interaction of virtual photons... If they exchaned energy real photon would be emitted and absorbed... And in case of virtual photons no energy is exchanged... Did I get it?
  5. Jul 23, 2012 #4
    you have to be careful about the two repelling eachother argument...

    how would a proton and electron attract eachother with that logic?
  6. Jul 23, 2012 #5


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    Welcome to PF!

    Hi Ezio3.1415! Welcome to PF! :smile:
    real photons are physics (they exist)

    virtual photons are just maths (they don't)
    no, they do so because of the fields

    the virtual photons in the maths help us to calculate the fields :wink:
  7. Jul 23, 2012 #6
    As tiny-tim explains, virtual photons appear in between the actual interactions, for the mathematical approach to QFT first used by Feynman. Normal photons enter into interactions (vertices of Feynman diagrams), and they can also emerge. As indicated by the name, you won't see one.
  8. Jul 24, 2012 #7
    Dipstick: I would say the same thing I guess... Interaction! :uhh:

    Tim: Thank you... Hope to get a lot of help here... The forum's so active... :)

    But I thought standard model visualizes the field with the help of field particles,doesn't it? Or is it just the maths? But it makes total sense... It explains why the range of forces with virtual particles(the force carriers) so well...

    Can u explain that without Feynman diagram? :confused:
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