Find the  momentum of a photon of ultraviolet radiation of $280nm$ wavelength.

Given,

$\lambda =280\times {10}^{-9}m$
Since, $E=\frac{hc}{\lambda }$

$\Rightarrow E=\frac{\left(4.316\times {10}^{-15}eVsec\right)\left(3\times {10}^{8}m{s}^{-1}\right)}{\left(280\times {10}^{-9}m\right)}=4.6eV$

Momentum of a photon is

$p=\frac{E}{c}$

$\Rightarrow p=\frac{4.6\times 1.6\times {10}^{-19}}{3\times {10}^8}=2.45\times {10}^{-27}kgm{s}^{-1}$