In-Class Demonstration of the Zeeman Effect: From Qualitative Observation to Quantitative Experiments

The Zeeman effect, a fundamental quantum phenomenon, demonstrates the inter-action between magnetic fields and atomic systems. While precise spectroscopic measure-ments of this effect have advanced significantly, there remains a lack of simple, visually ac-cessible demonstration for educational purposes. Here, we present a low-cost experiment that allows for direct visual observation of the Zeeman effect. Our setup involves a flame containing sodium (from table salt) placed in front of a sodium vapor lamp. When a magnetic field is applied to the flame, the shadow cast by the flame noticeably lightens, providing a clear, naked-eye demonstration of the Zeeman effect. Furthermore, we conduct two quanti-tative experiments using this setup, examining the effects of varying magnetic field strength and sodium concentration. This innovative approach not only enriches the experimental demonstra-tion for teaching atomic physics at undergraduate and high school levels but also provides an open platform for students to explore the Zeeman effect through hands-on experience.