Teaching Diffraction of Light and Electrons: Classroom Analogies to Classic Experiments

Diffraction and interference are phenomena that demonstrate the wave nature of light and of particles. Experiments relating to the diffraction/interference of light can easily be carried out in an educational lab, but it may be impossible to perform experiments involving electrons because of the lack of specialized equipment needed for such experiments. It would, however, be possible for students to analyze data from scientific experiments by analogy to experiments they themselves had performed. Based on this rationale, this paper describes two pairs of experiments that may be of interest to teachers aiming to teach the wave nature of light and of particles to upper secondary school (or to college) students. Specifically, students are asked to (i) carry out a double-slit experiment by using monochromatic light, thus repeating in a way the historical experiment of Young,¹ and then analyze real data from Jönsson's^2–3 scientific double-slit experiment with electrons, and (ii) perform an experiment involving diffraction of monochromatic light using a compact disc (CD) as a reflection grating, and then by analogy analyze data from the experiment of Davisson and Germer.⁴ The proposed real experiments are not original, and different versions of them have been wi dely described in the literature.^5,6 The educational value of the present work lies in the use of the analogy between experiments carried out in the school lab and experiments performed in the scientific lab.