The photoelectric effect is the emission of electrons or other free carriers when light hits a material. Electrons emitted in this manner can be called photoelectrons. This phenomenon is commonly studied in electronic physics, as well as in fields of chemistry, such as quantum chemistry and electrochemistry. To make sense of the fact that light can eject electrons even if its intensity is low, Einstein proposed that a beam of light is not a wave propagating through space, but rather a collection of discrete wave packets (photons). Wiki Quantum anything is imaginary. There is no such thing as photon particle/light quanta. Photoelectric effect theory won a Nobel Prize, but later Einstein admitted it was wrong. All these fifty years of conscious brooding have brought me no nearer to the answer to the question, 'What are light quanta?' Nowadays every Tom, D i c k and Harry thinks he knows it, but he is mistaken. -Albert Einstein 1954. In reality, light is alternating current coexisting with atoms/medium. If the frequency is high enough, it can vibrate electrons moving in solar cells and produce electric current. This is the true mechanism of photoelectric effect. There is no photon particle knocking electron with momentum.