With what velocity (in m/s) must an electron travel so that its momentum is equal to that of photon with a wavelength of $\lambda =5200\text{Å}$

$\begin{array}{l}\text{ Momentum of photon }p=\frac{h}{\lambda }=\frac{6.626\times {10}^{-34}}{5200\times {10}^{-10}}\mathrm{kgm}/\mathrm{s}\\ \text{ Momentum of electron }=mv=9.1\times {10}^{-31}v\end{array}$

where v is the velocity of electron.
Equating the two momenta, we have.

$9.1\times {10}^{-31}v=6.626\times {10}^{-34}/5200\times {10}^{-10}\Rightarrow v=1400\mathrm{m}/\mathrm{s}$