Q 12-12-126JEE MainJEE Main 2018 (8 Apr)Easy
If the series limit frequency of the Lyman series is $\nu_L$, then the series limit frequency of the Pfund series is:
Answer: (A) $\dfrac{\nu_L}{25}$
The series limit corresponds to a transition from $n = \infty$: $\nu \propto \dfrac{1}{n_f^2}$.
Lyman: $n_f = 1$; Pfund: $n_f = 5$. So
$$\nu_{\text{Pfund}} = \frac{\nu_L}{25}$$
Solution by Sreeraj P, M.Sc Physics