A photoelectron is an electron that is ejected from an atom or molecule when it absorbs energy from light, typically in the form of ultraviolet or X-ray radiation. This process is known as the photoelectric effect, which demonstrates the particle-like behavior of light. When the energy of the incoming photon exceeds the binding energy of the electron, the electron is released. The study of photoelectrons is important in fields like quantum mechanics and spectroscopy. By analyzing the energy and momentum of photoelectrons, scientists can gain insights into the electronic structure of materials and the interactions between light and matter. This has applications in material science and photovoltaics.