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The velocity of photon in media

  1. Aug 8, 2012 #1
    what is the velocity of photon in media, c or c/n ?
  2. jcsd
  3. Aug 8, 2012 #2
    I would assume that would depend on the media. Correct me if I'm wrong, but I think I remember reading something about the speed of light through a bose-einstein condensate being on the order of 17m/s, maybe 21m/s. Either way, very slow. Glass, water, plastic I'm sure all have slightly different values for c, but no where near the tens of m/s like some materials.
  4. Aug 8, 2012 #3
    Actually I am talking about common media with its refraction index given.
  5. Aug 8, 2012 #4
    That would be the sine of the angle wouldn't it?

    Or more specifically [itex]v_{2} = \frac{v_{1}sinθ_{2}}{sinθ_{1}}[/itex]
    Last edited: Aug 8, 2012
  6. Aug 8, 2012 #5


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    You are making a lot of assumptions about the nature of photons. There is no reason to treat them as little bullets, speeding from place to place. The whole essence of QM is not to think of photons as existing 'anywhere' except when they are emitted and detected.
  7. Aug 8, 2012 #6
    photons always move with speed c.the refractive index part just accounts for a phase shift for light.it does not mean that photon move at speed c/n.for further reference you can see feynman lectures vol.1('the origin of refractive index').
  8. Aug 8, 2012 #7
  9. Aug 8, 2012 #8


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    I'm not quite sure what you are saying, but I was near certain that light does in fact move slower through a medium such as glass, with V=c/n.
  10. Aug 8, 2012 #9


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    From the FAQ at the top of this forum:

    https://www.physicsforums.com/showthread.php?t=511177 [Broken]
    Last edited by a moderator: May 6, 2017
  11. Aug 9, 2012 #10
    the whole theory of refractive index came much later than the name refractive index.people have used it as a simplification for description of behaviour of light in a medium .if there is an electric field shining on a piece of glass it will induce oscillation
    of electrons(neglecting protons because they are more massive so there radiation can be neglected) which in turn will emit their own radiation which when combines with the original electric field will give rise to a phase shift of the electric field which can be described by giving light a speed c/n in that medium.
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