Photon emission in electronic transitions

[MuonMinus]

How would you explain, on a basic level, why only one photon (as opposed to two, three...) is emitted when an electron in an atom changes its energy level? This is for students with only introductory Physics background.

 

[DaveE]

I know this isn't the answer you're looking for, but...
That's how we observe that the universe works. We only ever see 1 photon. It's not just a glib answer, it is the difference between physics and philosophy or math.

 

[Andy Resnick]

How would you explain, on a basic level, why only one photon (as opposed to two, three...) is emitted when an electron in an atom changes its energy level? This is for students with only introductory Physics background.

At the introductory level it is indeed mysterious, especially since multiphoton absorption is a common laboratory technique. Multiphoton emission has been observed and reported on, but explanations 'why' photoemission is predominantly single-photon requires discussion of the 'selection rules' which are quantum and not introductory.