Question

When an electron of an atom returns from an excited state to the ground state, it emits energy in the form of a photon. How does the change in energy level compare to the energy of the emitted photon?
A)It is less than the energy of the photon.
B)It is about one third the energy of the photon.
C)It is exactly half of the energy of the photon.
D)It is equal to the energy of the photon
E)It is exactly twice the energy of the photon.

Answer 1

The levels in question are completely fixed in terms of their energy. So, if we have an electron at a higher level of a certain fixed energy (say E2) and it 'relaxes' down to a lower level, also of a fixed and defined energy (say E1), then the energy difference between the two levels must be fixed also. That is, the energy change (E2 - E1) that the electron must have undergone for it to drop down must be fixed.

It undergoes this specific change by being able to release a specific amount of energy in the form of a photon (a 'bundle' or 'packet' of energy) of light. So, the energy of the photon must be exactly equal to the energy change involved in the transition, and so (D.) must be the correct answer.

Answer 2

Nice explanation!

Answer 3

Energy is quantized, meaning that there are only certain energies that can be taken on and emitted.