The Photoelectric Effect
The maximum kinetic energy of electrons ejected from a metal surface by monochromatic light, is measured for several wavelengths. The value of Planck's constant, h, is derived by an analysis of the data in the light of Einstein theory of the photoelectric effect.
Lab Guide (PDF)

Photoelectric effect lab. (Image courtesy of Junior Lab staff.)
References
Melissinos, Adrian C. "Photoelectric Effect." In Experiments in Modern Physics. New York, NY: Academic Press, 1966.