The Wave Nature of Electrons (Edexcel International A Level Physics)

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Lindsay Gilmour



The Wave Nature of Electrons

  • Electron diffraction was the first clear evidence that matter can behave like light and has wave properties
    • This is demonstrated using the electron diffraction tube
  • The electrons are accelerated in an electron gun to a high potential, such as 5000 V, and are then directed through a thin film of graphite
    • The lattice structure of the graphite acts like the slits in a diffraction grating
  • The electrons diffract from the gaps between carbon atoms and produce a circular pattern on a fluorescent screen made from phosphor

Electron Diffraction Experiment, downloadable AS & A Level Physics revision notes

Electrons accelerated through a high potential difference demonstrate wave-particle duality 

  • In order to observe the diffraction of electrons, they must be focused through a gap similar to their size, such as an atomic lattice
  • Graphite film is ideal for this purpose because of its crystalline structure
    • The gaps between neighbouring planes of the atoms in the crystals act as slits, allowing the electron waves to spread out and create a diffraction pattern

  • The diffraction pattern is observed on the screen as a series of concentric rings
    • This phenomenon is similar to the diffraction pattern produced when light passes through a diffraction grating
    • If the electrons acted as particles, a pattern would not be observed, instead, the particles would be distributed uniformly across the screen

  • It is observed that a larger accelerating voltage reduces the diameter of a given ring, while a lower accelerating voltage increases the diameter of the rings

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Lindsay Gilmour

Author: Lindsay Gilmour

Lindsay graduated with First Class Honours from the University of Greenwich and earned her Science Communication MSc at Imperial College London. Now with many years’ experience as a Head of Physics and Examiner for A Level and IGCSE Physics (and Biology!), her love of communicating, educating and Physics has brought her to Save My Exams where she hopes to help as many students as possible on their next steps.

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