7A55.30 - Electron Diffraction
Demonstrate electron wave properties.
Electrons are emitted by the cathode at the back end of the tube. They are accelerated by a high voltage. They then strike a target of powdered graphite crystals, producing a characteristic circular diffraction pattern. The pattern can be seen when the diffracted electrons strike a phosphorescent coating at the front end of the tube. As the accelerating voltage is increased, decreasing the wavelength of the electrons, the circles become smaller.