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Refraction and Special Realitivity

  1. Apr 21, 2009 #1
    Hello, new comer to realitivity here.

    My friend and I were wondering if when light refracts if the photons temporarly convert back into partial mass.

    Through my understanding of e=(mc^2)/sqrt(1-v^2/c^2) it appears as if they would, but since photons have an infinite amount of energy backing them up, then is it even possible for them to even reach a stage of having mass?

    edit: sorry for my bad grammar, english has never been my strong point.
  2. jcsd
  3. Apr 21, 2009 #2


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    A photon can never have mass, but it is possible for a photon to convert into other particles which do have rest mass. I don't know exactly what happens when light refracts, but see post #4 here for a good discussion of why light slows down in a medium like water, basically involving the photons being repeatedly absorbed and re-emitted.
    No, photons only have a finite amount of energy--keep in mind that the "m" in that equation is the rest mass, which would be zero for a photon, so the equation just gives the undefined answer 0/0. To find the energy of a photon you have to use the quantum equation E=hf, where f is the photon's frequency and h is planck's constant.
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