The story of the photoelectric effect is an ongoing one, from its discovery in 1887 to its use in a myriad of today’s devices, such as cameras and cell phones. This program tells that story, charting the contributions of Hertz, Lenard, Planck, and Einstein, while making use of actual experiments, clever demonstrations, and formulas that describe each aspect of a crucial physics phenomenon. Topics include: Hertz’s initial experiment; Lenard’s investigations; evidence for a wave theory of light; problems with the wave theory; Planck’s explanation of black body radiation; Einstein’s explanation of the photoelectric effect; calculations of threshold frequency, cut-off potential, and work function; and real-world applications of the photo cell. (35 minutes)