Question

The kinetic energy of an electron is $4.55\times {10}^{-25}J$. Calculate the wavelength, $(h=6.6\times {10}^{-34}Jsec,massofelectron=9.1\times {10}^{-31}kg)$.

Answer 1

$KE=\frac{1}{2}m{v}^2=4.55\times {10}^{-25}$

or $\frac{1}{2}\times 9.1\times {10}^{-31}\times v^2=4.55\times {10}^{-25}$

or $v^2=\frac{2\times 4.55\times {10}^{-25}}{9.1\times {10}^{-31}}$

$v={10}^{3}m{s}^{-1}$

Applying de Broglie equation,

$\lambda =\frac{h}{mv}=\frac{6.6\times {10}^{-34}}{9.1\times {10}^{-31}\times {10}^3}=0.72\times {10}^{-6}m$.