Draw a neat labelled diagram of experimental arrangement of Davisson - Germer to study electron diffraction

Explanation

A copious supply of electrons may be obtained by connecting a tungsten filament coated with Barium oxide to a low D.C. voltage. Electrons are then accelerated by applying a high D.C. supply. A fine beam is made to fall on the Nickel target. A moveable collector connected to a galvanometer is moved towards the regions of diffraction. The entire apparatus is kept in vacuum. For the given angle between the incident and the scattered electron beam, the intensity of beam is measured.
For a known value of anode voltage, wavelength is measured using the formula lambda` = (12.27)/sqrt(V)` Å. It was noticed that a strong peak appeared in the intensity of scattered electrons for an accelerating voltage of 54V at a scattering angle `theta = 50 ^(@)`. For an lattice constant of `d=0.11`nm for Nickel, the value `lambda= d/(2sintheta)` agrees with the experimental result.

This confirms that electrons in motion behave as waves.