Question

The frequency of first line of Balmer series in hydrogen atom is $v_0$. The frequency of corresponding line emitted by singly ionised helium atom is -

• A. $2v_0$
• B. $4v_0$
• C. $v_0/2$
• D. $v_0/4$

Answer 1

Answer: (B)

$4v_0$

$v\propto Z^2\Rightarrow \frac{v_{H_2}}{v_{He}}={\left(\frac{1}{2}\right)}^2=\frac{1}{4}$

$\Rightarrow v_{He}=4v_{H_2}=4v_0$