Einstein's photoelectric effect

Einstein's photoelectric effect describes how light can cause electrons to be emitted from a material, typically a metal. When light of a specific minimum frequency shines on the surface, it transfers energy to the electrons. If this energy exceeds the electrons' binding energy, they are "knocked out" of the material, creating an electric current. Importantly, the energy of the emitted electrons depends on the light's frequency, not its brightness, supporting the idea that light consists of particles called photons with quantized energy. This discovery was crucial in developing quantum theory and understanding the particle-like nature of light.