Now,
E= 2.03 eV
Also,
Ef – Ei = E2 – E5
= -5.74 eV – (–3.71 eV)
= –2.03 eV.
From the conservation of energy, we know that the atom lost energy when that atom emitted the photon. Thus, the transition was from E5 to E2.
The energy levels for an atom are quantized.