2.50 The longest wavelength doublet absorption transition is observed at 589 and 589.6 nm. Calculate the frequency of each transition and energy difference between two excited states.

Frequency of radiation (ν),
v = 12.0 x 10-9 s
ν = 5.0 × 108 s-1
Energy (E) of source = Nhν
Where,
N = number of photons emitted
h = Planck’s constant ν =
frequency of radiation
Substituting the values in the given expression of (E):
E = (2.5 × 1015) (6.626 × 10-34 Js) (5.0 × 108 s-1)

E = 8.282 × 10-10 J
Hence, the energy of the source (E) is 8.282 × 10-10 J.