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Waves or Particles?

Einstein Explains the Photoelectric Effect


In 1905, Albert Einstein was working as a clerk at the Swiss Patent Office in Bern. He was completely unknown in the physics community. This was about to change as he published three seminal papers in a single journal volume during that year. As well as explaining the photoelectric effect, he also sought to prove the existence of atoms and introduced relativity. Not bad for a 26-year old!

To explain the photoelectric effect, Einstein reasoned that if the energy of oscillators was quantised as demonstrated by Planck, then the energy of electromagnetic fields (i.e.: light) could be given the same treatment. Up to this point, all phenomena involving light (such as diffraction) was explained in terms of waves. Now, Einstein's treatment meant the light could arrive in discrete packets - which he dubbed photons. Light now had a dual nature. Depending on the experiment, light behaved as either a particle or a wave!


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