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I'm having trouble finding sufficient answers that don't boil down to discussing materials.

Some people say that if a photon does not excite an electron it doesn't interact with it at all and just goes through the atom. Other people say that photons are always absorbed, it's just that if they don't have the "right" amount of energy they are immediately reemitted (and in this case I would like to know how: Are these photons emitted along the previous trajectory, along a new trajectory, both?). And are terms like "transmission" and "reflection" at all applicable to single atoms or do they only pertain to arrangements of atoms aka materials?

bansheenocturno
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  • I think this is at least partially covered by my answer to How do photons know they can or can't excite electrons in atoms?. Have a read through it and see what you think. – John Rennie Feb 04 '24 at 08:46
  • @JohnRennie Oh I guess it does clear up my confusion around the word "absorption" now. Your answer also points to the notion that there is a chance that a photon with the "just right" amount of energy won't even excite an electron if I understood that right. Now I'm curious if a photon can go through an atom without merging its wavefunction with the wavefunction of an electron from that atom. – bansheenocturno Feb 04 '24 at 09:04
  • There is always an interaction between the photon and the atom, so the wavefunctions always merge. But there is always a non-zero probability that the wavefunctions can evolve with time back into the photon and atom i.e. the end result is that the photon passed through the atom and nothing happened. – John Rennie Feb 04 '24 at 09:06
  • @JohnRennie Thank you, now at least the first part of my question is answered. – bansheenocturno Feb 04 '24 at 09:17
  • @JohnRennie Photons can: absorb, transmit, emit, reflect, refract, defract, scatter, polarize and interfere. All 9 interactions are due to the EM field. I think I covered them all? – PhysicsDave Feb 04 '24 at 13:18

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