DAVISON AND GERMER EXPERIMENT PDF

In the year , two American physicists C.J Davisson and L.H Germer conducted an experiment to explain the wave nature of electrons. Description: Davisson and Germer’s experiment was in the support of de Broglie’s hypothesis. They demonstrated the diffraction of electron beam similar to. Davisson Germer experiment with observations, Co-relating Davisson Germer experiment and de Broglie are provided here. Learn more about it at BYJU’S.

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The Davisson—Germer experiment was a experiment by Clinton Davisson and Lester Germer at Western Electric later Bell Labs[1] in which electrons, scattered by the surface of a crystal of nickel metal, displayed a diffraction pattern. This confirmed the ggermeradvanced by Louis de Broglie inof wave-particle duality, and was an experimental milestone in the creation of quantum mechanics. Geermer to Maxwell’s equations in the late 19th century, light was thought to consist of waves of electromagnetic fields and matter was thought to consist of localized particles.

Davisson–Germer experiment – Wikipedia

However, this was challenged in Albert Einstein ‘s paper on the photoelectric effectwhich described light as discrete and localized quanta of energy epxeriment called photonswhich won him the Nobel Prize in Physics in In Louis de Broglie presented his thesis concerning the wave—particle duality theory, which proposed the idea that all matter displays the wave—particle duality of photons.

An important contribution to the Davisson—Germer experiment was made by Walter M. This suggestion of Elsasser was then communicated by his senior colleague and later Nobel Prize recipient Max Born to physicists in England. When the Davisson and Germer experiment was performed, the results of the experiment were explained by Elsasser’s proposition.

Devission and Germer Experiment

However the initial intention of the Davisson and Germer experiment was not to confirm the de Broglie hypothesisbut rather to study the surface of nickel. The angular gerer of the reflected electron intensity was measured and was determined to have the same diffraction pattern as those predicted by Bragg for X-rays.

At the same time George Paget Thomson independently demonstrated the same effect firing electrons through metal films to produce a diffraction pattern, and Davisson and Thomson shared expefiment Nobel Prize in Physics in This, in combination with the Compton effect discovered by Arthur Compton who won the Nobel Prize for Physics in[5] established the wave—particle duality hypothesis which was a fundamental step in quantum theory.

Davisson began work in to study electron bombardment and secondary electron emissions.

Davisson–Germer experiment

A series of experiments continued through Davisson and Germer’s actual objective was to study the surface of adn piece of nickel by directing a beam of electrons at the surface and observing gemer many electrons bounced off at various angles.

They expected that because of the small size of electrons, even the smoothest crystal surface would be too rough and thus the electron beam would experience diffused reflection. The experiment consisted of firing an electron beam from an electron gunan electrostatic particle accelerator at a nickel crystal, perpendicular to the surface of the crystal, and measuring how the number of reflected electrons varied as the angle between the detector and the nickel surface varied.

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The electron gun was a heated filament that released thermally excited electrons which were then accelerated through an electric potential difference, giving them a certain amount of kinetic energy, towards the nickel crystal. To avoid collisions of the electrons with other atoms on their way towards the surface, the experiment was conducted in a vacuum chamber. To measure the number of electrons that were scattered at different angles, a faraday cup electron detector that could be moved on an arc path about the crystal was used.

The detector was designed to accept only elastically scattered electrons. During the experiment, air accidentally entered the chamber, producing an oxide film on the nickel surface.

To remove the oxide, Davisson and Germer heated the specimen in a high temperature oven, not knowing that this caused the formerly polycrystalline structure of the nickel to form large single crystal areas with crystal planes continuous over the width of the electron beam.

When they started the experiment again and the electrons hit abd surface, they were scattered by nickel atoms in crystal planes so the atoms were regularly spaced of the crystal. This, ingenerated a diffraction pattern with unexpected peaks. geemer

On a break, Davisson attended the Oxford meeting of the British Association for the Advancement of Science in summer At this meeting, he learned of the recent advances in quantum mechanics.

To Davisson’s surprise, Max Born gave a lecture that used diffraction curves from Davisson’s research which he had published in Science that year, using the data as confirmation of the de Broglie hypothesis. He learned that in prior years, other scientists — Walter Elsasser, E. Dymond, and Blackett, James Chadwick, and Charles Ellis — had attempted similar diffraction experiments, but were unable to generate low enough vacuums or detect the low-intensity beams needed.

Returning to the United States, Davisson made modifications to the tube design and detector mounting, adding azimuth in addition to colatitude. Questions still needed to be answered and experimentation continued through By varying the applied voltage to the electron gun, the maximum intensity of electrons diffracted by the atomic surface was found at different angles.

As Max von Laue proved inthe periodic crystal structure serves as a type of three-dimensional diffraction grating. The angles of maximum reflection are given by Bragg’s condition for constructive interference from an array, Bragg’s law. As Davisson and Germer state in their follow-up paper, “These results, including the failure of the data to satisfy the Bragg formula, are in accord with those previously obtained in our experiments on electron diffraction.

The reflection data fail to satisfy the Bragg relation for the same reason that the electron diffraction beams fail to coincide with their Laue beam analogues. Davisson and Germer’s accidental discovery of the diffraction of electrons was the first direct evidence confirming de Broglie’s hypothesis that particles can have wave properties as well.

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Davisson’s attention to detail, his resources for conducting basic research, the expertise of colleagues, and luck all contributed to the experimental success. It wasn’t until the s that vacuum tubes were adequately made reliable and available to expand on the electron diffraction technique, but since that time, scientists have used LEED diffraction to explore the surfaces of crystallized elements and the spacing between atoms.

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