Question

Find the wave number of a photon having an energy of $2.072eV$
Given: Charge on electron $=1.6\times {10}^{-19}C$
Velocity of light in air $=3\times {10}^{8}m/s$
Planck's constant$=6.63\times {10}^{-34}J-s$

Answer 1

$E=\frac{hc}{\lambda }$
$\therefore \lambda =\frac{hc}{E}=\frac{6.63\times {10}^{-34}\times 3\times {10}^8}{2.072\times 1.6\times {10}^{-19}}=6\times {10}^{-7}m$
Wave number $\overline{v}=\frac{1}{\lambda }$
$\Rightarrow \frac{1}{6\times {10}^{-7}}=1.67\times {10}^6{m}^{-1}$