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Davisson Germer Experiment

The electron shows dual nature means the particle nature and the wave nature both. Davisson and Germer have established the wave nature of slow moving electron in 1927.Davisson Germer experiment 


germer ExprimentSet up of Davisson Germer experimentIn the experimental set up Davisson and Germer there is a filament of tungsten coated with barium oxide, which on heating with the electric current from a battery emits large number of electrons. There is a hollow metallic cylinder with a hole along the axis. 


This hollow metal cylinder surrounds the filament and is kept at negative potential, so that the electrons emitted from filament may form a convergent beam of electrons. The hollow metallic cylinder acts as cathode. The other cylinder with a fine hole along its axis is kept at positive potential with respect to the cathode, acts as anode. The cathode and the anode form an electron gun, by which a fine beam of electrons can be obtained under different accelerating potentials applied between cathode and anode. 


 There is a nickel crystal cut along the cubical diagonal and one more instrument is electron detector rotating on a circular scale and is connected to a sensitive galvanometer to record the amount of current.Working of Davisson Germer experimentA fine beam of accelerated electrons obtained from electrons gun is made to fall normally on the surface of nickel crystal. The electrons are scattered in different directions by the atom of crystal. The rotating detector detects the intensity of the electron beam. 


The intensity of the scattered beam is measured for the different values of scattering angle `phi` . The angle between the incident and the scattered electron beam. For angle `phi` = 50° and potential difference of anode is 54 Volt, if we calculate the wavelength of the electron wave, it is equal to 1.65 Angstrom. Accordingly, to the de Broglie wavelength the wave associated with electron having wavelength is equal to 1.66 Angstrom.ConclusionThe Davisson Germer experiment shows that there is a very close relation with the estimated value of de Broglie wavelength and the experimental value. This proves the existence of de Broglie waves for the slow moving electrons.