The mass of electron =  $9.1\times {10}^{-31}\mathrm{kg}$. If its $\mathrm{K}.\mathrm{E}.=4.55\times {10}^{-25}\mathrm{J}$, then its wavelength is

$\mathrm{\lambda }=\frac{\mathrm{h}}{\mathrm{mV}}=\frac{\mathrm{h}}{\sqrt{2\mathrm{mE}}};\mathrm{E}=\mathrm{KE}\mathrm{of}\text{\hspace{0.33em}\hspace{0.33em}electron}$

$\lambda =\frac{h}{\sqrt{2\times 9.1\times {10}^{-31}\times 4.55\times {10}^{-25}}}=\frac{h}{9.1\times {10}^{-28}}$

$=\frac{6.625\times {10}^{-34}}{9.1\times {10}^{-28}}=7.2\times {10}^{-5}=0.72\times {10}^{-6}=7.2\times {10}^{-5}m$