$\therefore \,\bar v = \frac{1}{\lambda } = R\left[ {\frac{1}{{n_1^2}} - \frac{1}{{n_2^2}}} \right] = R\left[ {\frac{1}{{n_1^2}} - \frac{1}{{{\infty ^2}}}} \right] = \frac{R}{{n_1^2}}$
$\because \,\bar v = 12186.3 = \frac{{109677.76}}{{n_1^2}}$
$ \Rightarrow n_1^2 = \frac{{109677.76}}{{12186.3}} = 9 \Rightarrow {n_1} = 3$
The line belongs to Paschen series.
(આપેલ : હાઈડ્રોજન પરમાણુના પ્રથમ કક્ષામાં (કોશમાં) ઈલેક્ટ્રોનની ઉર્જા $-2.2 \times 10^{-18}\,J ; h =6.63 \times 10^{-34}\,Js$ અને $c =3 \times 10^{8}\,ms ^{-1}$ )
$\mathop {CH_3^ + }\limits_{\rm{I}} $ $\mathop {{H_3}{O^ + }}\limits_{{\rm{II}}} $ $\mathop {N{H_3}}\limits_{{\rm{III}}} $ $\mathop {CH_3^ - }\limits_{{\rm{IV}}} $