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.