Question

In terms of Rydberg constant $R$, the wave number of the first Balmer line is

• A. $R$
• B. $3R$
• C. $\frac{5R}{36}$
• D. $\frac{8R}{9}$

Answer 1

Answer: (C)

Wave number $\bar{v}=\frac{1}{\lambda }=R\left(\frac{1}{n_1^2}-\frac{1}{n_2^2}\right)$
Here, $n_1=2,n_2=3$
$\therefore \bar{v}=\frac{5R}{36}$