Question

The wavelength of the first line of Lyman series is $\lambda$. The wavelength of the first line in Paschen series is ______

• A. $108/7$
• B. $27/5$
• C. $7/108$
• D. $5/27$

Answer 1

Answer: (A)

$\frac{1}{{\lambda }_1}=R\left(\frac{1}{1^2}-\frac{1}{2^2}\right)$
$\frac{1}{{\lambda }_1}=R\left(\frac{1}{3^2}-\frac{1}{4^2}\right)$
$\frac{{\lambda }_1}{\lambda }=\frac{\frac{3}{4}}{\frac{7}{16\times 9}}$
${\lambda }_1=\frac{3}{4}\times \frac{16\times 9}{7}\lambda$
${\lambda }_1=\frac{108}{7}\lambda$