The photoelectric effect demonstrates that light behaves as a particle, as evidenced by the ejection of electrons from a material when illuminated by photons of sufficient energy. This phenomenon, first observed by Heinrich Hertz and explained by Albert Einstein, shows that the energy of a photon is proportional to its frequency, with higher-frequency light resulting in higher-energy ejected electrons. The intensity of light affects the number of electrons emitted, as more photons lead to more interactions with electrons, but does not change their energy. The interaction occurs at the individual particle level, meaning that the superposition of light and electron waves does not contribute to electron ejection. Overall, the photoelectric effect provides compelling evidence for the particle nature of light.