Photoelectric Effect

About This Experiment

The photoelectric effect demonstrates the quantum nature of light. Einstein explained that light consists of photons with energy E = hf. When photons strike a metal surface, electrons are emitted only if the photon energy exceeds the work function φ of the metal. The maximum kinetic energy is KEmax = hf - φ.

Classical wave theory could not explain why increasing light intensity doesn't increase electron energy, or why there's a threshold frequency below which no electrons are emitted regardless of intensity. This experiment provided crucial evidence for wave-particle duality and earned Einstein his Nobel Prize.