Question

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

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

Answer 1

The correct option is D $743nm$

Absorbed energy $=$ Emitted energy

$\frac{hc}{\lambda }=\frac{hc}{{\lambda }_1}+\frac{hc}{{\lambda }_2}$

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

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

${\lambda }_2=743nm$.