103 Electron Diffraction

The electron diffraction experiment demonstrates the wave nature of electrons. An electron with momentum p has a de Broglie’s wavelength of λ=h/p. When a beam of electrons is passed through a crystalline structure (such as graphite), an interference pattern of bright and dark rings is formed. If the electrons are accelerated to higher momentum (by turning up the accelerating voltage), the electrons’ wavelength will decrease. The separation between the bright and dark rings will thus decreases. (similar to fringe separation in the double slit experiment being dependent on wavelength Δy=Lλ/d)

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• 18 Quantum Physics