Question

What is the minimum energy that must be given to a H atom in ground state so that it can emit an $H_{\gamma }$ line in Balmer series ?

• A. 13.06 eV
• B. 12.75 eV
• C. 10.2 eV
• D. 2.86 eV

Answer 1

Answer: (A)

$H_{\gamma }$ line in the Balmer series corresponds to transition from $n=5$ to $n=2$.
Therefore, electron in the ground state $(n=1)$ must be raised first to the state $(n=5)$.
The minimum energy required for this purpose is $E=E_5-E_1$
$=-\frac{13.6}{5^2}eV-\left(-\frac{13.6}{1^2}eV\right)$ (As $E_n=-\frac{13.6}{n^2}eV$)
$=-0.54eV+13.6eV=13.06eV$