Question

What is the wave number of $4^{th}$ line in Balmer series of hydrogen spectrum? $(R=1,09,677c{m}^{-1})$

• A. $24,630c{m}^{-1}$
• B. $24,360c{m}^{-1}$
• C. $24,730c{m}^{-1}$
• D. $24,372c{m}^{-1}$

Answer 1

Answer: (D)

$\bar{v}=R\left(\frac{1}{n_1^2}-\frac{1}{n_2^2}\right)$
For Balmer series, $n_1=2$ and for $4^{\text{th }}$ line in Balmer series $n_2=6$
$\because R=109677c{m}^{-1}$
$\bar{v}=109677\left(\frac{1}{2^2}-\frac{1}{6^2}\right)$
$=109677\left(\frac{1}{4}-\frac{1}{36}\right)$
$\bar{v}=24,372c{m}^{-1}$