Question

What voltage must be applied to an electron microscope to produce electrons of $\lambda =1.0A$?

• A. 190 volt
• B. 180 volt
• C. 160 volt
• D. 150 volt

Answer 1

The correct option is D 150 volt

Energy gained when subjected to voltage, $V$ is given as $E=eV$

So wavelength will be $\lambda =\frac{h}{\sqrt[2]{22mE}}$ so $\frac{h^2}{{\lambda }^2}=2mE=2m\left(eV\right)$ so volatge $V=\frac{h^2}{2me{\lambda }^2}$

Where $h$ is planck's constant and $m$ is mass of electron.

Putting all values we get $V=\frac{(6.62\times {10}^{-34}Js{)}^2}{2\times 9.1\times {10}^{-31}Kg\times 1.6\times {10}^{-19}C\times ({10}^{-10}meter{)}^2}=150.49Volt$

Option D is correct.