The first four spectral lines in the Lyman series of a H-atom are = 1218 Å, 1028Å, 974.3 Å and 951.4Å. If instead of hydrogen, we consider deuterium, calculate the shift in the wavelength of these lines.
Let us take as the reduced masses of electron of hydrogen and as the reduced masses of electron of deuterium.
we know that
As ni and nf are fixed for by mass series for hydrogen and deuterium
From equation (i) and (ii)
Reduced mass for hydrogen,
Reduced mass for deuterium,
where M is mass of the proton
From (iii) and (iv)