Question

Find the de-Broglie wavelength of an electron with kinetic energy of $120eV$.

• A. $95pm$
• B. $102pm$
• C. $112pm$
• D. $124pm$

Answer 1

The correct option is C $112pm$

Given : $K=120eV$

Mass of electron $m=9.1\times {10}^{-31}$ kg

de-Broglie wavelength $\lambda =\frac{h}{\sqrt{2mK}}$

$\therefore$ $\lambda =\frac{6.6\times {10}^{-34}}{\sqrt{2\times 9.1\times {10}^{-31}\times 120\times 1.6\times {10}^{-19}}}$

Or $\lambda =\frac{6.6\times {10}^{-34}}{59.1\times {10}^{-25}}=0.112\times {10}^{-9}$ $m=112$ $pm$