The Photoelectric Effect

The photoelectric effect occurs when light shining on a metal surface causes electrons to be ejected from that surface. The energy of the light photons determines whether electrons are released; only light with enough energy (a certain frequency) can free electrons. This discovery showed that light behaves like particles (photons) carrying quantized energy, which was key evidence for quantum theory. Essentially, the effect demonstrates that light can transfer energy to electrons, resulting in their emission, and highlights the particle-like properties of light in understanding atomic behavior.