Electron diffraction

A particle doesn’t diffract, but a wave does.

Because we usually model an electron as a particle, we wouldn’t expect it to be able to diffract - but it does.

The experiment

If we pass a ray of electrons at a high voltage, for example, 5,000V, through a sheet of graphite, and the graphite has a double slit diffraction arrangement, then we’ll see the electrons diffract and form rings around a central bright spot.

That shows that electrons can behave like a wave!

This shows something called wave particle duality.

Diffraction and voltage

• If we increase the voltage of the electron beam, then the electrons are diffracted less - so they spread out less.
• Similarly, if we decrease the voltage of the electron beam, then the electrons are diffracted more - so they spread out more.