Joanne_Park_4C wrote:How does the photoelectric effect exactly prove that light doesn't act as waves but as particles?
I think its because when they were attempting to eject electrons with light, they knew that the light needed to carry with it enough energy to eject the electron. So when they weren't getting the electrons ejected with the light source they were using, they decided to increase the energy by, so they thought, increasing the intensity (amplitude), much like a more intense ocean wave will have lot more energy than a small ocean wave. They then realized that increasing the intensity does nothing when electrons were previously not being ejected, but increasing the frequency of the light does cause electrons to eject. Not completely sure how they arrived to this, and not completely sure I'm correct, but this told them that light was not acting like a wave in this experiment, but like a particle, and to eject the electron we need to increase the energy of the particles (photons) themselves. Then Einstein discovered, through these observations, that E=hv, stating that the energy of a photon is proportional to the frequency of the light for that photon. So increasing the frequency was actually increasing the energy, showing that light was acting as a particle in this experiment.
They also found that increasing the intensity is only increasing the amount of photons, not the energy. So, if the light actually did have a high enough frequency to eject an electron, increasing the intensity would just cause more electrons to be ejected, based off of the 1 photon per 1 electron ratio.
Hope this helps, sorry if I'm not fully correct!