primary photoelectric effect

The primary photoelectric effect occurs when light shines on a metal surface, causing electrons to be emitted from it. The energy of the incoming light (photons) must be high enough to overcome the metal’s work function—the minimum energy needed to release an electron. When this condition is met, electrons are ejected instantly, with their kinetic energy proportional to the light's frequency, not its intensity. This phenomenon demonstrated that light behaves as particles (photons), providing key insights into quantum physics and the particle-like nature of light.