Question

Describe the Davission-Germer experiment by using the schematic diagram to show electron diffraction.

Answer 1

The Davisson-Germer experiment demonstrated the wave nature of the electron, confirming the earlier hypothesis of de Broglie. This experiment gave establishment of quantum mechanics and Schrodinger wave equation.

Davisson and Germer designed and built a vacuum apparatus for the purpose of measuring the energies of electrons scattered from a metal surface. Electrons from a heated filament were accelerated by a voltage and allowed to strike the surface of nickel metal. The electron beam was directed at the nickel target, which could be rotated to observe angular dependence of the scattered electrons. Their electron detector was mounted on an arc so that it could be rotated to observe electrons at different angles. It was a great surprise to them to find that at certain angles there was a peak in the intensity of the scattered electron beam. This peak indicated wave behaviour for the electrons and could be interpreted by the Bragg law to give values for the lattice spacing in the nickel crystal.

Using the Bragg law, the de Broglie wavelength expression, and the kinetic energy of the accelerated electrons gives the following relationship:

In the historical data, an accelerating voltage of 54 volts gave a definite peak at a scattering angle of 50°, giving the electrons kinetic energy of 54 eV. So this experiment proved the de-Broglie hypothesis and Braggs equation.this also brought a revolution in quantum mechanics.

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