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Does photon exist without velocity c ?

  1. May 14, 2013 #1
    recently i have been struggling with the concept if photon exists without traveling at velocity c ? i knew c is constant only when it travels trough space and when it travels through other medium with refractive indexes it does not exist at all .. is it true ?
    how do scientists define why photons exists?
    or what changes occur to a photon when it passes through other mediums except vacuum?
    plz help
  2. jcsd
  3. May 14, 2013 #2
    photons always travel a speed 'c'...they are born that way and die that way: instantaneously.
    They don't accelerate and decelerate as do mass particles.

    For a discussion try here:


    From post #7 there:

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