Matter/Electron Waves and the Davisson-Germer Experiment

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SUMMARY

The Davisson-Germer Experiment demonstrates electron diffraction, revealing that electrons exhibit wave-like properties when scattered by a crystalline nickel target. The experiment's findings indicate that while electron diffraction peaks are most pronounced at a perpendicular incidence angle (90°), they can still occur at other angles due to the principles of constructive interference as described by Bragg's law. The initial confusion regarding the necessity of a 90° angle stems from its simplicity in calculations, but it is not a strict requirement for observing diffraction peaks. Understanding the relationship between the angle of incidence and diffraction patterns is crucial for interpreting the results of this experiment.

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  • Understanding of electron diffraction and wave-particle duality
  • Familiarity with Bragg's law and its application in crystallography
  • Knowledge of the Davisson-Germer Experiment and its historical context
  • Basic concepts of angles of incidence and glancing angles in physics
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  • Study the principles of electron diffraction in detail
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Physics students, researchers in quantum mechanics, and anyone interested in the wave-particle duality of electrons and the implications of electron diffraction in material science.

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Homework Statement



This is a conceptual question that I am not quite sure about. In the Davisson-Germer Experiment (details here), do the electron diffraction peaks that occur only show up if the incident beam of electrons hits the crystal surface perpendicularly?

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The Attempt at a Solution



I was really confused when reading this in my textbook when it relates to this question. The book talks a lot about Davisson and Germer's initial intent which was to "attempt to understand the arrangement of atoms on the surface of a nickel sample by elastically scattering a beam of low-speed electrons from a polycrystalline nickel target. (If you are unfamiliar with the story, someone dropped a flask of liquid air on the vacuum system, oxidizing the nickel target. They then realized that the crystalline structures it created scattering of electrons, showing that the electron is also a matter-wave).

However, in my textbook, they talk about \alpha being the target orientation, and that is 90°. After that brief mention, they do not really speak of it again. Because of this, I am a little unsure as what to believe. Would these peaks arise if the angle was different than 90°?
 
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Wikipedia has this 90° in its story too. But they refer to Bragg's law for the angles. There the pictures have angle of incidence = exit angle. I think perpendicular incidence isn't essential, but it gives a nice expression for angles of constructive interference.
 
That is what I thought as well. I thought that the 90 degree angle makes it "easier" - like the simplest case of what actually happens. However, I did not know if there was an actual reason why it does or does not matter.

Thank you.
 
What is glancing angle?
I found this definition but I am not getting this.
the angle between a ray incident on a plane surface and the surface,as of a beam of electrons incident on a crystal;the complement of the angle of incidence.
 

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