Davisson and Germer Experiment

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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.

Fig. 1

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.

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