Photoelectric Effect and Experiment

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Saachi_Kotia_4E
Posts: 68
Joined: Fri Sep 28, 2018 12:23 am

Photoelectric Effect and Experiment

Postby Saachi_Kotia_4E » Tue Oct 09, 2018 10:11 am

Can someone explain what the photoelectric experiment and effect are in simpler terms? I had a hard time following the lecture.

Tam To 1B
Posts: 72
Joined: Fri Sep 28, 2018 12:25 am

Re: Photoelectric Effect and Experiment

Postby Tam To 1B » Tue Oct 09, 2018 2:43 pm

In the photoelectric experiment, light was shone on a metal surface. If the energy of the incoming light was greater than the energy needed to remove the electron (work function), then electrons were emitted from the surface. This way, we are able to measure their kinetic energy.(Ephoton - Ework function = Ekinetic)
If the light had a long wavelength that did not give off enough energy, then it did not emit electrons. Increasing the intensity of that light surprisingly did not eject electrons either. For that reason, in this experiment, light was then needed to be seen as a photon (a packet of energy) rather than as a wave. This means that light with shorter wavelength and higher frequency eject electrons. If it was a wave model, then a greater intensity would mean a greater amplitude should eject electrons, but this wasn't the case.
Energy of each photon of light must be greater than or equal to the energy needed to remove the electron in order for electrons to be ejected from the surface.

Kristen Kim 2K
Posts: 70
Joined: Fri Sep 28, 2018 12:16 am

Re: Photoelectric Effect and Experiment

Postby Kristen Kim 2K » Tue Oct 09, 2018 2:51 pm

Basically the photoelectric effect is when light (UV) is shined onto a metal surface, electrons in the metal surface become excited and they get emitted. Scientists did an experiment on this thinking that the more intense the light, the more electrons will be emitted. But they were proved wrong because the number of electrons being emitted weren't completely proportional to the intensity of the light. They were basing the experiment off of classical mechanics, where things are more continuous, but this effect could only be explained by quantum mechanics, where things are more discrete. They later found that the number of electrons being emitted depends on the frequency (wavelength) of the light rather than the intensity (amplitude). That explains why even light that is low in intensity can emit a lot of electrons off the metal surface, because it has a high frequency. On the other hand, light shined onto the metal won't emit as many electrons even if it's high in intensity, because the frequency is too low and doesn't have enough energy to emit electrons. This is explained by the fact that light is made up of photons, which are specific amounts of energy, and the amount of energy in each photon is related to the frequency of the light (UV radiation).


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