this post was submitted on 04 Jul 2023
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Light travels at different speeds through different mediums (air, glass, water...etc). In some materials it can move incredibly slow. Why is this?
In simple terms. A photon is absorbed by an electron, moving it from a ground state and up an orbital to an excited state. The electron then falls back down to it's ground state re-imitting the photon, which then gets re-absorbed by another electron on another atom....etc
For more: https://en.m.wikipedia.org/wiki/Spectroscopy
I'm just a layman, but find topics about how the world around us works to be fascinating.
Re-emission can result in extremely large refractive indices, but the weirder explanation for the refractive index is the one responsible for all the ones we experience on a regular basis. It relies on the wave property of light. If an electromagnetic wave is traveling through a medium, it will weakly jiggle the surrounding atoms, ever so slightly polarizing them. This polarization is moving charge, which creates its own electromagnetic wave. The medium's wave will be shifted slightly in phase, causing destructive interference with the wave traveling through it and slowing the wavefront.
This explanation explains why you can have even a low-energy photon, which can't knock an electron to its next highest energy level still be slowed.
That's pretty cool, thanks for sharing