ON THE PRESENTATION OF WAVE PHENOMENA OF ELECTRONS WITH THE YOUNG–FEYNMAN EXPERIMENT

The Young-Feynman two-hole interferometer is widely used to present the electron wave-particle duality and in particular the buildup of interference fringes with single electrons. The teaching approach consists of two steps: i) electrons come through only one hole but diffraction effects are disregarded; ii) electrons come through both holes and interference fringes are described. Therefore, a student might believe that wave phenomena are not revealable in case i) but they arise only by the combined effect of electrons from the two holes. To avoid misunderstanding regarding the distribution of electrons passing through one hole, Fresnel and Fraunhofer diffraction patterns are discussed. In particular, an original experiment, realized with a standard electron microscope and a sample with round holes is presented to introduce the wave nature of electrons. The experimental results clearly show that a careful discussion of electron diffraction phenomena from one hole provides students with the evidence that the interference experiment from both holes is not strictly required to show the superposition of electron waves.