A Class Demonstration That Provides a Simple, Quick Experimental Determination of Planck’s Constant

Nearly every high school and college introductory chemistry course features a treatment of Planck’s constant. This naturally arises in the context of studying the Bohr model of the atom and the nature of the electron─Planck’s constant is key to explaining atomic emission/absorption spectra, which provide evidence for the quantized energy levels for electrons. In this study, we sought to implement an interactive demonstration that provides a simple, straightforward determination of Planck’s constant by showing how the energy of a photon correlates with its frequency. The class demonstration used a hand-held module that facilitated the measurement of band gap voltage for several differently colored LEDs. The demonstration is best suited for high school and first-year college chemistry students and can be performed in approximately half an hour.