Answer:

The electron in the ground state of H-atom jumps to the nth state after absorbing the radiation.

Wavelength of the radiation, λ=970A

o

=970×10

−10

m

Energy gained by the electron, E

′

=

eλ

hc

eV=

970×10

−10

1.237×10

−6

=12.75eV

Thus the energy of the n

th

state, E

n

=−13.6+12.75=−0.85eV

Using: E

n

=

n

2

−13.6

eV

∴ −0.85=

n

2

−13.6

⟹n=4

Number of (emission) spectral line, N=

2

n(n−1)

=

2

4(4−1)

=6 lines

The ratio of wavelengths of the last line of Balmer series and the last line of Lyman series is