Ionization potential of hydrogen atom is $$13.6eV.$$  Hydrogen atom in ground state are excited by monochromatic light of energy $$12.1\,eV.$$  The spectral lines emitted by hydrogen according to Bohr's theory will be

Solution :
After absorbing $$12.1\,eV$$  the electron in $$H$$ $$atom$$  is excited to 3 shell.
$$\eqalign{ & {E_n} - {E_1} = \frac{{ - 13.6}}{{{n^2}}} - \left( { - 13.6} \right) = 12.1 \cr & \frac{{ - 13.6}}{{{n^2}}} + 13.6 \cr & = 12.1 \cr & \therefore \,\,n = 3 \cr} $$
The possible transitions are = 3