Davisson and Germer Experiment :-
The wave nature of electrons was first experimentally verified by C. J. Davisson and L. H. Germer in 1927 and independently by G. P. Thomson in 1928.
The experimental arrangement consists of an electron gun which comprises of a tungsten filament ‘F’ , coated with barium oxide and heated by a low voltage power supply. Election emitted by the filament are accelerated to a desired velocity by applying suitable potential from a high voltage power supply. They are made to pass through a cylindrical with fine holes along its axis, producing a fine collimated beam. The beam is made to fall on the surface of Nickel crystal.
- The electrons are scattered in all directions by the atoms of the Crystal. The intensity of the electron detector (collector). The detector can be moved on a circular scale and is connected the galvanometer which record the current.
- The deflection of the galvanometer is proportional to the intensity of the electron beam, entering the collector.
- The experiment was performed by varying the accelerating voltage from 44 volt to 68 volt. it was noticed that a strong peak appeared in the intensity ‘I’ for an accelerating voltage of 54 volt at scattering angle θ =50⁰
From the electron diffraction measurements the wavelength of matter waves was found to be 0.165 nm
The de Broglie wavelength λ associated with electrons, using equation
λ = h/p = 1·227/√V nm
for V = 54 volt
λ = 1·227/√54 = 0·167 nm
Thus Davisson – Germer experiment strikingly confirms the wave nature of electrons and de Broglie relation.