The extreme wavelengths of Paschen series are

0.365 µm and 0.565 µm 0.818 µm and 1.89 µm 1.45 µm and 4.04 µm 2.27 µm and 7.43 µm

0.818 µm and 1.89 µm

ln Paschen series $\frac{1}{\lambda_{\max }}=R\left[\frac{1}{(3)^2}-\frac{1}{(4)^2}\right]$ $\Rightarrow \lambda_{\max }=\frac{144}{7 R}=\frac{144}{7 \times 1.1 \times 10^7}=1.89 \times 10^{-6} \mathrm{~m}=1.89 \mu \mathrm{m}$ Similarly $\lambda_{\min }=\frac{9}{R}=\frac{9}{1.1 \times 10^7}$ = 0.818 µm