The photons don't slow down. It's the phase velocity that slows down because the electrons in the medium rearrange themselves in the presence of electromagnetic radiation, causing interference reducing the phase velocity of a wave. This is why the dielectric constant is related to the polarizability of a medium.
It's more about how fast communication can happen within the medium. The Cerenkov radiation happens because electrons can't "find out" about the charged particle coming through, creating a shock, similar to a sonic blast or the wake of a boat.
Hopefully I got this more or less right... I build detectors to look for Askarayan emission (a related phenomenon in the radio) but I'm definitely not a theorist :).
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The photons don't slow down. It's the phase velocity that slows down because the electrons in the medium rearrange themselves in the presence of electromagnetic radiation, causing interference reducing the phase velocity of a wave. This is why the dielectric constant is related to the polarizability of a medium.
It's more about how fast communication can happen within the medium. The Cerenkov radiation happens because electrons can't "find out" about the charged particle coming through, creating a shock, similar to a sonic blast or the wake of a boat.
Hopefully I got this more or less right... I build detectors to look for Askarayan emission (a related phenomenon in the radio) but I'm definitely not a theorist :).