Number of possible spectral lines which may be emitted in bracket series in H atom, if electrons present in $9^{th}$ excited level returns to ground level is:

The correct option is C 45

The option marked is incorrect. the correct option is C

No. of spectral lines = $\frac{(n_2-n_1)(n_2-n_1+1)}{2}$

Where,

$n_2$ - Higher level from which the electron comes - 13

$n_1$ - Lower level to which the electron returns - 4 (For Bracket series)

No. of spectral lines = $\frac{(13-4)(13-4+1)}{2}$

= $\frac{9\times 10}{2}$ = 45