Ionization potential of hydrogen atom is `13.6 V`. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy `12.1 eV`. The spectral lines emitted by hydrogen atoms according to Bohr's theory will be

Explanation

Ionisation energy corresponding to ionisation potential
=-13.6 eV
Photon energy incident =12.1 eV
So, the energy of electron in excited state
=-13.6+12.1=-1.5 eV
`.i.e.," E_(n)=(-13.6)/(n^(2)) eV`
`-1.5=(-13.6)/(n^(2))rArrn^(2)=(-13.6)/(-1.5)=9rArrn=3`
i.e., the energy of electron in excited state corresponds to third orbit.
The possible spectral lines are when electron jumps from orbit 3rd to 2nd 3rd to 1st and 2nd to 1st. Thus, three spectral lines are emitted.