5 ms·
It's probably that photons always propagate at c and that the apparent change of speed of light in glass is caused by photon absorption and delayed reemission b
by red75prime 3y ago
It's probably that photons always propagate at c and that the apparent change of speed of light in glass is caused by photon absorption and delayed reemission by atoms (at least it's how perturbation theory of quantum electrodynamics describes the process).
- eternauta3k 3y agoDo you really need photons and quantum stuff though? "Just" learn about how dielectric materials work + how EM waves work from Griffiths and then everything will make sense.
- red75prime 3y agoDepends on what you want. A useful approximation, or the latest approximation that is closer to how it really is.
- eternauta3k 3y agoWhat insight is being gained by going with the more complex model? You can work out a lot using classical EM and predict a bunch of cool optical/diffraction phenomena without a lot of math, and the math you do is crystal clear. QFT or even just QM+time-dependent perturbations are a pain in the ass in comparison.
- red75prime 3y agoIf you have engineering mindset (how to do something), then, sure, you are better off with the most useful approximation. If you have scientific mindset (how things are), then practical usefulness of the model of reality is secondary.
- bcbrown 3y agoI'm looking at Griffiths right now, and 9.3 Electromagnetic Waves in Matter states (emphasis in the original): "Since [the dielectric constant] is almost always greater than 1, light travels more slowly through matter - a fact that is well known from optics." I'm still confused. How is it an inaccurate simplification to state that the speed of light in glass is lower than in a vacuum?
- eternauta3k 3y agoI wouldn't call it inaccurate at all. I think it's a perfectly good model. You can explain the phenomena otherwise using a more detailed model, but you don't need to.