Abstract: In the experimental teaching of the photoelectric effect, the Planck constant can be calculated by measuring the cutoff voltage at different frequencies, thus verifying the correctness of Einsteins equations and deepening the understanding of the quantum properties of light. Einsteins equation for the photoelectric effect shows that the cutoff voltage is a function of the frequency of the light and is independent of the intensity of the light. However, the change in cutoff voltage was found to be related to the light intensity, because the light intensity affects the number of photoelectrons emitted. However, once saturation is reached, the light intensity no longer affects the cutoff voltage. In addition, the existence of dark current will also affect the measurement of cutoff voltage, resulting in errors. Systematic analysis of these factors helps students to fully understand the photoelectric effect and its quantum properties.

Key words: photoelectric effect, planck constant, cutoff voltage