Photoelectric effect  can  be explained  by

Quantum theory of light can explain the photoelectric effect that if a quanta of photon is incident on the metal surface, the energy of photon breaks the electron-nucleus interaction and thus an electron is emitted from the metal surface. Since some energy is required to break that interaction to emit the electron, so the photoelectric effect takes place from the metal surface only if the energy of photon is greater than the work function of that metal.