Question

A stream of electrons from a heated filament was passed between two charged plates kept at a potential difference V esu. If e and m are charge and mass of an electron, respectively, then the value of $\frac{h}{\lambda }$ (where $\lambda$ is wavelength associated with electron wave) is given by:

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

Kinetic energy of electron is = e × V

As per de-Broglie's equation

$\lambda =\frac{h}{\sqrt{2m{E}_k}}=\frac{h}{\sqrt{2meV}}$
$\therefore \frac{h}{\lambda }=\sqrt{2meV}$