Question

The energy required to excite an electron of H-atom from first orbit to second orbit is :

• A. $\frac{3}{4}$ of its ionisation energy
• B. $\frac{1}{2}$ of its ionisation energy
• C. $\frac{1}{4}$ of its ionisation energy
• D. none

Answer 1

The correct option is A $\frac{3}{4}$ of its ionisation energy

$I.P.=E_{\infty }-E_1=-E_1$
$\Delta E=E_2-E_1=\frac{E_1}{4}-E_1$
=$-\frac{3}{4}{E}_1=\frac{3}{4}IP$