When an electron de-excites from the third quantum level to the second, and then to the ground state, two photons are emitted. The sum of the emitted frequencies equals the frequency of the single photon that would be emitted if de-excitation were from the third to
A)the second level.
B)the ground state.
C)any other level.
D)none of the above

Question

Quizplus · Accepted Answer

The energy difference between the third and second levels is not enough to emit a photon with the same frequency as the de-excitation from the third level to the ground state. Therefore, the de-excitation must occur in two steps, emitting two photons with frequencies that add up to the frequency of the photon emitted in a single step from the third level to the ground state. De-excitation from the third level to any other level would emit photons with different frequencies than those emitted in the two-step process to the ground state.

When an Electron De-Excites from the Third Quantum Level to the Second