40. Electron Diffraction

The set-up below is an excellent demonstration of the wave nature of particles. An electron beam is passed through a carbon foil and the resulting diffraction rings displayed on the fluorescent screen of the tube. (Since the graphite crystals are randomly oriented, the diffraction pattern is rings.) From the accelerating voltage, DeBroglie's wavelength, and the diffraction ring diameter, you can calculate the atomic spacing of carbon.

The students don't know what they are seeing. You take that into the class room and the students see green rings, but a physicist sees something astonishing, the wave nature of matter.
-Prof. George Igo