1)

Electron in hydrogen atom first jumps from third excited state to second excited state and then from second excited to the first excited state. The ratio of the wavelength λ1: λ2 emitted in the two cases is


A) 7/5

B) 27/20

C) 27/5

D) 20/7

Answer:

Option C

Explanation:

The wave number ($\bar{v}$) of the radiation = $\frac{1}{\lambda}$

= $R_{\infty}\left[\frac{1}{n_1^2}-\frac{1}{n_2^2}\right]$

Now for case (I) n1= 3, n2= 2

$\frac{1}{\lambda_{1}}=R_{\infty}\left[\frac{1}{9}-\frac{1}{4}\right]$

 R=  Rydberg constant

$\frac{1}{\lambda_{1}}=R_{\infty}\left[\frac{4-9}{36}\right]$

$=\left[\frac{-5R_{\infty}}{36}\right]$

$\lambda_{1}=\left[\frac{-36}{5R_{\infty}}\right]$

$\frac{1}{\lambda_{2}}=R_{\infty}\left[\frac{1}{4}-\frac{1}{1}\right]$

= $\left[\frac{-3R_{\infty}}{4}\right]$

$\lambda_{2}=\left[\frac{-4}{3R_{\infty}}\right]$

$\frac{\lambda_{1}}{\lambda_{2}}=\frac{-36}{5R_{\infty}}\times\frac{3R_{\infty}}{-4}$

$\frac{\lambda_{1}}{\lambda_{2}}$ = $\frac{27}{5}$