Some energy levels of a molecule are shown in the figure. The ratio of the wavelengths $r = \lambda_1/\lambda_2$, is given by : <br> <img src="http://clay6.com/mpaimg/1187_a.jpg "/>
( A ) $r = \frac{4}{3}$
( B ) $r= \frac{2}{3}$
( C ) $r = \frac{3}{4}$
( D ) $r = \frac{1}{3}$