Question

An electron is in the third excited state. How many different photon-wave lengths are possible?​

Answer 1

Answer:

One or two. Maybe three.

Two different wavelengths can be emitted by a bound electron in the third level of excitation. The first occurs as the electron drops to the second state.

The second occurs as it drops from the second to the first state. But it could be argued that this wavelength doesn’t count, because the electron isn’t in the third state when it emits this photon.

In theory it should be able to drop directly from the third to the first state, emitting a single photon of shorter wavelength. But I don’t know that this ever occurs. It does happen in reverse: an electron can skip an energy level by absorbing a photon whose wavelength is equivalent to the sum of both energy differences.