Hydrogen atom in ground state is excited by a monochromatic radiation of λ=975Å. Number of spectral lines in the resulting spectrum emitted will be
Energy provided to the ground state electron
=6.6x3/975 x 10-16
=0.020x10-16=2 x 10-18
It means the elctron is jump to n=3 from n=1 The number of field lines possible from n=3 to n=1 is 2.
n→3, to n→2 to n→1