Q. The extreme wavelengths of Paschen series are
A) $0.365\mu m$ and $0.565\mu m$
B) $0.818\mu m$ and $1.89\mu m$
C) $1.45\mu m$ and $0.04\mu m$
D) $2.27\mu m$ and $7.43\mu m$
Explanation
(b) In Paschen series $\frac{1}{\lambda_{\max}} = R\left\lbrack \frac{1}{(3)^{2}} - \frac{1}{(4)^{2}} \right\rbrack$
$\Rightarrow \lambda_{\max} = \frac{144}{7R} = \frac{144}{7 \times 1.1 \times 10^{7}} = 1.89 \times 10^{- 6}m = 1.89\mu m$
Similarly $\lambda_{\min} = \frac{9}{R} = \frac{9}{1.1 \times 10^{7}} = 0.818\mu m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.