Question

The wave number of the $H_{\alpha }-$line in Balmer series of hydrogen spectrum is:

• A. $\frac{5R}{36}$
• B. $3R$
• C. $\frac{21R}{100}$
• D. $\frac{3R}{4}$

Answer 1

Answer: (A)

$\frac{5R}{36}$

$H_{\alpha }$ line Balmer series means 3 $\to$ 2 transition

we know $v^{-}=R(1/n_1^2-1/n_2^2)$ here $v^{-}=$ wave number

$v^{-}=R(1/2^2-1/3^2)$

$v^{-}=R(1/4-1/9)$

$v^{-}=\frac{5R}{36}$