Question

A gas absorbs a photon of 335 nm and emits radiations of two wavelengths. If one of the radiations is at 680 nm, then the other is at:

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

Answer 1

The correct option is C 743 nm

Energy of the absorbed photon = Sum of the enrgies of the emitted photons
$\frac{hc}{\lambda }=\frac{hc}{{\lambda }_1}+\frac{hc}{{\lambda }_2}\frac{1}{\lambda }=\frac{1}{{\lambda }_1}+\frac{1}{{\lambda }_2}\frac{1}{355\times {10}^{-9}}=\frac{1}{680\times {10}^{-9}}+\frac{1}{{\lambda }_2}$
${\lambda }_2=\frac{1}{1.346\times {10}^6}=742.76\times {10}^{-9}m=743nm\left(Approx\right)$