Question

A light of wavelength 1218 A${}^o$ is emitted when the electron of a hydrogen atom drops from fifth to third quantum level. Find the wavelength of the photon emitted when electron falls fro third to ground level?

• A. 1025 $A^0$
• B. 2050 $A^0$
• C. 1320 $A^0$
• D. 2460 $A^0$

Answer 1

The correct option is A 1025 $A^0$

For n${}_5$ $\to$ n${}_3$
$\frac{1}{\lambda }$ = R[$\frac{1}{n_2^2}$ - $\frac{1}{n_1^2}]$
$\frac{1}{12818}$ =R[$\frac{1}{9}$ - $\frac{1}{25}$]
R = $\frac{9\times 25}{16\times 12818}$ A
For n${}_3$ $\to$ n${}_1$
$\frac{1}{\lambda }$ = R[$\frac{1}{1^2}$ - $\frac{1}{3^2}$] = $\frac{9\times 25}{16\times 12818}$ $\frac{8}{9}$
$\therefore$ $\lambda$ = 1025 A${}^o$