EM radiation inside atoms

Question

If atom is composed largely of "empty" space what happens INSIDE the atom when immersed in EM radiation? Does the EM wave propagate INSIDE the atom? For example, gas atoms in space, a radio wave goes thru the gas cloud but does it go "thru" the space inside the gas atoms? ( the word "thru" is problematic..but best word I could think of ).

Answer 1

Yes, external EM wave permeates all space its wavefront reaches, there is no way for the atom to shield its interior from it.

This is known to be true due to both theoretical reasons - Maxwell's equations and QM equations are linear, all waves are present everywhere and obey superposition; and experimental results - both electrons and nuclei can interact with external EM waves. For example, in NMR or MRI (NMR for imaging), radio-frequency EM waves interact with spins of hydrogen nuclei and some other nuclei, exchange energy with them and change their state.

Answer 2

Your question seems to imply that you are surprised that EM radiation can travel inside an atom because it is empty space, but you are OK with EM radiation traveling through space that contains gas atoms.

If that is the case (and you would be in good company), there are a number of misconceptions. The space inside atoms in no different to the space outside atoms, and EM fields permeate all of space. In fact, atoms have no edge - they kind of fade away as you get further from the nucleus so even asking about the difference is a meaningless question.

I would be wary about building a mental model of an atom as being a foam of electrons and photons and protons and exotica. Those mental models are inspired by Feynman but their subtleties require considerable sophistication.

Answer 3

"If atom is composed largely of "empty" space" This sentence is correct at high school level. what I mean is that is a simplified picture. Inside atom (let's say hydrogen) is full of photons! these photons fields are exchanged between the proton and electron and this exchange of photons creates what you call electric field.

"what happens INSIDE the atom when immersed in EM radiation"? When if the EM radiation is very energetic it can collide with the photons and create new particle. if is is weak, it can pass through the atom with out interacting with anything.

**"gas atoms in space, a radio wave goes thru the gas cloud" ** definitely not. when you start to study the atoms and photon, quantum mechanics and quantum field theories start to play a significant role. A lot of things can happen. the electron can absorb the photon, the protons can absorb the photon. if you have a lot of energy you can create new particles.