Question

A gas absorbs a photon of $355nm$ and emits at two wavelengths. If one of the emissions is at $680nm$, the others is at:

• A. $743nm$
• B. $518nm$
• C. $1035nm$
• D. $325nm$

Answer 1

The correct option is A $743nm$

Given that, $\lambda =355mn$

${\lambda }_1=680nm$ and ${\lambda }_2=?$

Hence, $\frac{1}{\lambda }=\frac{1}{{\lambda }_1}+\frac{1}{{\lambda }_2}$

$\frac{-1}{{\lambda }_2}=\frac{680-355}{680\times 355}$

$\frac{1}{355}=\frac{1}{680}+\frac{1}{{\lambda }_2}$

So,$\frac{1}{{\lambda }_2}=\frac{325}{241400}$

${\lambda }_2=743nm$

Therefore, the correct option is $A$