(N/A) The different series observed in the hydrogen spectrum are:
$1$. Lyman series: $\frac{1}{\lambda} = R \left( \frac{1}{1^2} - \frac{1}{n^2} \right)$,where $n = 2, 3, 4, \dots$
$2$. Balmer series: $\frac{1}{\lambda} = R \left( \frac{1}{2^2} - \frac{1}{n^2} \right)$,where $n = 3, 4, 5, \dots$
$3$. Paschen series: $\frac{1}{\lambda} = R \left( \frac{1}{3^2} - \frac{1}{n^2} \right)$,where $n = 4, 5, 6, \dots$
$4$. Brackett series: $\frac{1}{\lambda} = R \left( \frac{1}{4^2} - \frac{1}{n^2} \right)$,where $n = 5, 6, 7, \dots$
$5$. Pfund series: $\frac{1}{\lambda} = R \left( \frac{1}{5^2} - \frac{1}{n^2} \right)$,where $n = 6, 7, 8, \dots$
The general Rydberg formula for the wave number $\bar{\nu} = \frac{1}{\lambda}$ is:
$\bar{\nu} = R \left( \frac{1}{n_1^2} - \frac{1}{n_2^2} \right)$
where $R$ is the Rydberg constant $(1.097 \times 10^7 \ m^{-1})$,$n_1$ is the lower energy level,and $n_2$ is the higher energy level $(n_2 > n_1)$.