Question

The energy (in $eV$ ) required to excite an electron from $n=2$ to $n=4$ state in hydrogen atom is

• A. $-0.85$
• B. $+4.25$
• C. $-3.4$
• D. $+2.55$

Answer 1

Answer: (D)

$+2.55$

Answer 2

We know that, $E_{n}=\frac{13.6}{n^{2 \, \, }}$ $eV$ According to question, the required energy is $E=E_{2}-E_{4}$ $\frac{13.6}{\left(\right. 2 \left.\right)^{2}} - \frac{13.6}{4^{2}} = \frac{13.6}{4} - \frac{13.6}{16} \, eV$ $=\frac{\left(13.6 \times 4\right) - 13.6}{16}$ $eV$ $=\frac{40.8}{16}=+2.55$ $eV$