Question

The longest wavelength line in Lyman series of hydrogen atom spectrum will be
($R_H=$ Rydberg constant)

• A. $\frac{3R_H}{4}$
• B. $\frac{4}{R_H}$
• C. $\frac{1}{R_H}$
• D. $\frac{4}{3R_H}$

Answer 1

The correct option is D $\frac{4}{3R_H}$

Answer (4)
For longest wavelength in Lyman series, $n_1=1$ and $n_2=2$
$\frac{1}{\lambda }=R_H[\frac{1}{n_1^2}-\frac{1}{n_2^2}]$
$=R_H[\frac{1}{(1{)}^2}-\frac{1}{(2{)}^2}]=R_H[1-\frac{1}{4}]$
$\frac{1}{\lambda }=R_H\left[\frac{3}{4}\right]$
$\lambda =\frac{4}{3R_H}$