Question

The ratio of the shortest wavelength of two spectral series of hydrogen spectrum is found to be about 9. The spectral series are:

• A. Paschen and P fund
• B. Lyman and Paschen
• C. Brackett and Piund
• D. Balmer and Brackett

Answer 1

Answer: (B)

$\frac{\frac{1}{\lambda_{2}} = R_{H} \left(\frac{1}{n_{1}^{2}} - \frac{1}{n_{2}^{2}}\right)Z^{2}}{ \frac{1}{\lambda_{1}} = R_{H} \left(\frac{1}{m_{1}^{2}} - \frac{1}{m_{2}^{2}}\right)Z^{2}} $
as for shortest wavelengths both $n_2$ and $m_2$ are $\infty$
$ \therefore \frac{\lambda_{1}}{\lambda_{2}} = \frac{9}{1} = \frac{m_{1}^{2}}{n_{1}^{2}} $
Now if $m_1$ = 3 & $n_1$ = 1 it will justify the statement hence correct answer is Lyman and Paschen.