What phenomenon does the photoelectric effect explain?

The photoelectric effect is a phenomenon that demonstrates the particle nature of light, supporting the concept that light consists of discrete packets of energy known as photons or quanta. When light of sufficient frequency strikes the surface of a material, it can eject electrons from that material, which is a behavior that aligns well with the idea of light interacting as particles rather than as continuous waves.

The experimental observations of the photoelectric effect showed that the energy of emitted electrons depends on the frequency of the incoming light, not its intensity, which reinforces the quantized nature of light. Furthermore, this phenomenon helped establish the dual nature of light, suggesting that it exhibits both wave-like and particle-like properties, but in the context of the photoelectric effect specifically, it is the particle aspect that is emphasized.