Quote:
Originally Posted by absael
Now, to further complicate matters, I'll add that I was under the impression that a transparent material passes light because it (ideally) contains no atoms with electrons having energy levels matching those of photons of the wavelength at which the material is transparent, so no photons are absorbed. If this is the case, would light travel more slowly through a perfectly transparent medium?
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There are various ways of describing the QM interaction between the photon wavefunction and the electron shells of the atoms in the transparent medium.
One way, which tells the story as if we could actually find a specific photon interacting with a specific atom at a specific moment, makes sense of the above quite nicely. I've offered it a few time on BAUT. Here's a snippet from a previous post:
Quote:
Originally Posted by grant hutchison
The photon is said to hang up in the "dressed state" of the atom. If the photon has an energy close to an absorption line of the atom it's interacting with, it can "borrow" the necessary additional energy under the terms of Heisenberg's Uncertainty Principle, for a period of time inversely proportional to the amount of energy in the shortfall.
Most conventional transparent materials have absorption lines just "out of sight" in the UV. Since blue photons have to "borrow" less energy than red photons in order to match the energy of the UV absorption lines, blue photons can participate in the dressed state for longer than red photons: hence the speed of light is slower and the refractive index correspondingly higher for blue photons than red photons.
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Grant Hutchison