An electron is moving with a kinetic energy of  $4.55\times {10}^{-25}\mathrm{J}\text{.}$ Its de-Broglie wavelength (in nm) is

$\left(m_e=9.1\times {10}^{-31}kg,h=6.63\times {10}^{-34}Js\right)$

$\mathrm{\lambda }=\frac{\mathrm{h}}{\sqrt{2{\mathrm{m}}_{\mathrm{e}}{\mathrm{KE}}_{\mathrm{e}}}}$

$\mathrm{\lambda }=\frac{6.63\times {10}^{-34}}{\sqrt{2\times 9.1\times {10}^{-31}\times 4.55\times {10}^{-25}}}=\frac{6.63\times {10}^{-34}}{9.1\times {10}^{-28}}$

$\mathrm{\lambda }=\frac{6.63\times {10}^{-34}}{9.1\times {10}^{-28}}=0.728\times {10}^{-6} \mathrm{m}$

$\mathrm{\lambda }=0.728\times {10}^{-6}=0.7285\times {10}^9 \mathrm{nm} =728.5 \mathrm{nm}$