Fast electrons are diffracted from a polycrystalline layer of graphite: interference rings appear on a fluorescent screen. The interplanar spacing in graphite is determined from the diameter of the rings and the accelerating voltage.
Tasks
To measure the diameter of the two smallest diffraction rings at different anode voltages.
To calculate the wavelength of the electrons from the anode voltages.
To determine the interplanar spacing of graphite from the relationship between the radius of the diffraction rings and the wavelength.