The de Broglie wavelength of an electron (mass = $1×10^{-30}kg$, charge = $1.6×10^{-19}C$) with a kinetic energy of 200 eV is (Planck’s constant = $6.6×10^{-34}Js$)

$8.25×10^{-11}m$

de Broglie wavelength associated with charged particle

$λ=\frac{h}{\sqrt{2mE}}$

Here, $m=1×10^{-30}kg,e=1.6×10^{-19}C$

E = 200 eV and $h=6.6×10^{34}Js$

$∴λ=\frac{6.6×10^{-34}}{\sqrt{2×1×10^{-30}×200×1.6×10^{-19}}}=\frac{6.6}{8}×\frac{10^{-34}}{10^{-24}}=8.25×10^{-11}m$