3 ms·

That's not correct, but a widely held view. The speed differs to the properties of the EM field in these materials, not due to absorption.

kgwgk 9y ago
How do you explain the properties of the EM field in different materials in terms of photons, electrons, etc?
- mjburgess 9y ago
  How do you explain the magnetic and dielectric constants of free space? With great difficulty. cf. https://en.wikipedia.org/wiki/Permittivity https://en.wikipedia.org/wiki/Permittivity
  - kgwgk 9y ago
    Edit: maybe I didn't understand what is the "incorrect, but widely held view" you talked about.
    - mjburgess 9y ago
      Yes, the electronic structure of a crystalline material. That is one dimension of the "optical dielectric function" which is to do with the directionality of variation. Light is the motion of magnetic and electric fields, the "ease" of this motion is affected by a variety of factors. The speed of light depends not only on electric, but also magnetic field formation. And of each kind, there are a variety factors. The vacuum itself resits electromagnetic motion to some degree. I was observing that it isnt the case that light simply has one speed, the field in which it travels itself is damped.
      - kgwgk 9y ago
        Ok, probably you will agree with the "Speed of light through glass is ~2e5 km/s, but photons are still travelling at 3e5 km/s." I guess you object to the "The speed of light, that is the speed of a photon, is a constant" part, where he identifies "light" with "photons".
        comboy 9y ago
        Wow, I've been afk for a day and you answered so many comments, thank you, I've learned something. And yes, I should have left the speed of light out of the last sentence, my bad.
        kgwgk 9y ago
        To be fair, the speed of a free photon is c but when the photon is interacting it may not make sense to keep talking about its intrinsic speed. In any case, I feel objections to what you said should come from a “better” QED description and not from a “lower-level” classical description.

kgwgk 9y ago

How do you explain the properties of the EM field in different materials in terms of photons, electrons, etc?

mjburgess 9y ago
How do you explain the magnetic and dielectric constants of free space? With great difficulty. cf. https://en.wikipedia.org/wiki/Permittivity https://en.wikipedia.org/wiki/Permittivity
- kgwgk 9y ago
  Edit: maybe I didn't understand what is the "incorrect, but widely held view" you talked about.
  - mjburgess 9y ago
    Yes, the electronic structure of a crystalline material. That is one dimension of the "optical dielectric function" which is to do with the directionality of variation. Light is the motion of magnetic and electric fields, the "ease" of this motion is affected by a variety of factors. The speed of light depends not only on electric, but also magnetic field formation. And of each kind, there are a variety factors. The vacuum itself resits electromagnetic motion to some degree. I was observing that it isnt the case that light simply has one speed, the field in which it travels itself is damped.
    - kgwgk 9y ago
      Ok, probably you will agree with the "Speed of light through glass is ~2e5 km/s, but photons are still travelling at 3e5 km/s." I guess you object to the "The speed of light, that is the speed of a photon, is a constant" part, where he identifies "light" with "photons".
      - comboy 9y ago
        Wow, I've been afk for a day and you answered so many comments, thank you, I've learned something. And yes, I should have left the speed of light out of the last sentence, my bad.
        kgwgk 9y ago
        To be fair, the speed of a free photon is c but when the photon is interacting it may not make sense to keep talking about its intrinsic speed. In any case, I feel objections to what you said should come from a “better” QED description and not from a “lower-level” classical description.