Teaching the Photoelectric Effect Using an Open-Source Interactive Simulation

The photoelectric effect is one of the fundamental experiments that established the basis of quantum mechanics. Students studying this experiment in modern physics courses struggle to understand what it actually measured and why it is significant. This lesson is built around the PhET interactive simulation of this experiment. The activity involves the use of this open-source online simulation to carry out simulated experiments exploring the emission of electrons from metal surfaces when light is shone on them, and to compare those results with the predictions of the classical theory of light and its interactions with matter. This shows why Einstein’s quantum interpretation is needed to explain the observed behavior. Students complete a worksheet that guides them through the simulated experiment and comparison of observations with predictions of the classical theory of light and matter interactions. Then they are given the quantum interpretation, including exploring analogies to help develop their understanding. This presentation is supported by having students answer and discuss a set of questions in small groups. This lesson has achieved greatly improved student mastery of this fundamental experiment and how it shaped physics.