What is the true energy required to excite an atomic electron?

[Maurice Morelock]

TL;DR Summary

Is electronic excitation caused by a single wave or multiple waves in a given time period?

Energy is equal to Planck’s constant times the number of waves in 1 sec. The time scale for electronic excitation is far shorter then one second. So when we talk about the excitation of an electron from a lower level to a higher level occurring at a certain energy, are we talking about the exciting photon as a single wave with the amplitude equal to the number of waves in one sec?

 

[PeroK]

Summary:: Is electronic excitation caused by a single wave or multiple waves in a given time period?

Energy is equal to Planck’s constant times the number of waves in 1 sec. The time scale for electronic excitation is far shorter then one second. So when we talk about the excitation of an electron from a lower level to a higher level occurring at a certain energy, are we talking about the exciting photon as a single wave with the amplitude equal to the number of waves in one sec?

A full description of the excitation of an atom by a photon requires an analysis using QFT and, in particular, the quantization of the EM field.

https://en.wikipedia.org/wiki/Quantization_of_the_electromagnetic_field

The simplest description using only QM has a single photon of precisely the correct energy being absorbed by the atom and then a photon of the same energy being subsequently emitted. This is, however, not the whole story.