comes from: quantum physics: particles are waves
J. Clinton in 1937 Davisson and George P. Thomson received the Nobel for showing the interference patterns electrons, thus proving that the particle behaves like a wave. De Broglie had derived an equation for the electron had a wavelength that depended on his speed.
This wavelength is in range of a few angstroms, the distance separating two atoms in a solid. This wavelength also corresponds to X-ray photons, radiation and was used to study the structure of matter in crystallography.
If the electron had to behave like a wave, was expected to follow the same equations as for x-rays A crystalline solid is arranged in an orderly fashion: the atoms are arranged in equidistant planes. When a wave reaches a solid, is reflected in each of these planes. As each plane is deeper in the sample, it generates each traveling a different space reflection. At the end of the sample if the difference of these paths coincides with a multiple of the wavelength, then the interference produced are constructive, and the signal is stronger. In addition to the distance between planes, the difference between ways depends on the angle of incidence of the wave, so only certain angles where the interference is constructive.
This theory is summarized in an equation, Bragg's Law:
The wavelength depends on the angular momentum of electrons. This angular momentum is communicated by accelerating particles by a voltage V, to acquire a kinetic energy
For the same acceleration voltage value displayed various angles, for all integer multiples n. Davisson conducted their experiments on a nickel foil. Instead of changing the angle of incidence and detection, it was more convenient to vary the accelerating voltage, and maintain a fixed angle of detection at 50 °.
Each time the voltage reaches the relationship deduced from Bragg's Law, there is a peak in the graph
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