In 1905, Albert Einstein published a paper describing his discovery of the photoelectric effect where a photon acts like a particle.
Einstein proposed that for some purposes light can be regarded as made up of photon particles.
In 1905, Einstein was the first to propose that energy quantization was a property of electromagnetic radiation itself. Although he accepted the validity of Maxwell's theory, Einstein pointed out that many anomalous experiments could be explained if the energy of a Maxwellian light wave were localized into point-like quanta that move independently of one another, even if the wave itself is spread continuously over space.
In 1909 and 1916, Einstein showed that, if Planck's law of black-body radiation is accepted, the energy quanta must also carry momentum , making them full-fledged particles.
The 1921 physics Nobel prize was awarded to Einstein in most famous for his theory of relativity, but it is his discovery of photons that is mentioned by the Swedish Academy.
This photon momentum was observed experimentally by Arthur Holly Compton, for which he received the Nobel Prize in 1927.
He verified experimentally by Milikan’s studies of the photoelectric effect in 1914 – 16.
Discovery of Photon
