Question

A near UV photon of 300 nm is absorbed by a gas and then re-emitted as 2 photons. One photon is red with wavelength 760 nm. Hence wavelength of the second photon is:

• A. 460 nm
• B. 1060 nm
• C. 496 nm
• D. 300 nm

Answer 1

The correct option is C

496 nm

$\lambda$ = 300 nm

${\lambda }_1$ = 760 nm

${\lambda }_2$ = ?

Since the total energy has to be constant - $h\nu$ is constant, $\nu$ = $\frac{c}{\lambda }$

Use the formula: $\frac{1}{\lambda }=\frac{1}{{\lambda }_1}+\frac{1}{{\lambda }_2}$