Question

Which has a higher energy, a photon of violet light with wavelength $4000\mathring{A}$ or a photon of red light with wavelength $7000\mathring{A}$?

$[h=6.62\times {10}^{-34}Js]$

Answer 1

We know that, $E=hv=h\cdot \frac{c}{\lambda }$
Given, $h=6.62\times {10}^{-34}Js$, $c=3\times {10}^{8}m{s}^{-1}$
For a photon of violet light,
$\lambda =4000\mathring{A}=4000\times {10}^{-10}m$
$E=6.62\times {10}^{-34}\times \frac{3\times {10}^8}{4\times {10}^{-7}}=4.96\times {10}^{-19}J$
For a photon of red light,
$\lambda =7000\mathring{A}=7000\times {10}^{-10}m$
$E=6.62\times {10}^{-34}\times \frac{3\times {10}^8}{7000\times {10}^{-10}}=2.83\times {10}^{-19}J$
Hence, photon of violet light has higher energy than the photon of red light.