Following in Einstein's Footsteps: Teaching the Photoelectric Effect

Five years ago when I was asked to develop a module on quantum physics for a new course,¹ I decided to see if students could reproduce some of the reasoning that won Einstein his Nobel Prize. The students were in the third semester of a four-semester sequence emphasizing guided discovery, graphical analysis, and scientific communication. Most had weak high school physics backgrounds and had shown little evidence of remembering the concepts they had been exposed to at that level. The students were accustomed to working in groups of three to five for two-hour in-class workshops. They had not studied concepts related to light, optics, or electromagnetism in the course to that point. Thus, I gave them a workshop that presented a description of the photoelectric effect experiment at a schematic level (light of various colors hits a metal, electrons come off, the number of electrons and the kinetic energy per electron are measured), and a data table consisting of the qualitative color of the incident light, the intensity of the light, the number of electrons, and the kinetic energy per electron. The workshop asked them to graph the data in whatever way they felt appropriate, and to suggest a model of light that could explain the results.