Why is the speed of photons different?

[GREENMONKEY]

TL;DR

I read the Feynman's book about the quantum electrodynamics and I realized, that he was talking about the different speed of photons - please why are photons travelling at different speed, the blue photons are faster that the red ones, for instance?

Hi,

I read the Feynman's book about the quantum electrodynamics and I realized, that he was talking about the different speed of photons. I know, that the light travel's "slower" in a material, but he is also talking about the different speed of photons. I read on the web, that some photons travel's faster than the ther ones because of different energy, but WHY? Please give me some deep answer - deep like Feynman's book, no less.

 

[phinds]

please why are photons traveling at different speed, the blue photons are faster that the red ones, for instance?

I think you must have misunderstood something. "red" and "blue" are just different frequencies in the EM spectrum and they all travel at the same speed, c (in a vacuum).

 

[EPR]

This is why the speed of light you have read about is measured in vacuum(c).
In other mediums, due to different diffraction coefficients certain wavelengths are affected differently.

 

[PeterDonis]

I read on the web

Where? Please give a reference.

 

[DrClaude]

https://en.wikipedia.org/wiki/Dispersion_(optics)