Answer
$3.315\times 10^{-24}$ $kg.m/s$
Work Step by Step
The de Broglie wavelength $(\lambda)$ is express by the formula,
$\lambda=\frac{h}{p}$
where $h$ is the planck's constant and $p$ is the momentum of the moving particle.
$\therefore$ $p=\frac{h}{\lambda}$
Here, the photon has a wavelength of $\lambda=0.20$ $nm$
$\therefore$ The momentum of the photon is given by
$p=\frac{6.63\times 10^{-34}}{0.20\times 10^{-9}}$ $kg.m/s$
or, $p=3.315\times 10^{-24}$ $kg.m/s$
