## Intensity Proportional to Number of Photons?

JTieu_1L
Posts: 93
Joined: Wed Sep 30, 2020 9:34 pm

### Intensity Proportional to Number of Photons?

In Professor Lavelle's lecture, he stated that the intensity is proportional to the number of photons, but I thought it would be the energy in each photon and not the number; since it is a one photon to one electron interaction. Can someone please clarify this for me please?

Sarah_Hoffman_2H
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### Re: Intensity Proportional to Number of Photons?

Intensity is proportional to the number of photons. The energy in a photon is completely different. This is what proves light acts like a particle, because, as demonstrated in the photoelectric effect, increasing the intensity of the light did not have an effect on ejecting electrons.

Wasila Sun 2I
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### Re: Intensity Proportional to Number of Photons?

Intensity is proportional to the number of photons and can be described as the number of photons that pass a given area per second. So as the intensity increases, the # of photons increases too.

In the lecture, Dr. Lavelle mentions that increasing the intensity of a light source DOES NOT increase the energy per photon and will not emit electrons if the original energy of the photon isn't enough to overcome work (the threshold energy). To emit electrons in that scenario, one would need to change the light source to one that has photons with more energy.

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### Re: Intensity Proportional to Number of Photons?

I was a bit confused on this too. Does increasing the number of photons increase the energy, or does it not affect the energy since changing the intensity of light didn't result in more emitted electrons?

Helena Xu 1I
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### Re: Intensity Proportional to Number of Photons?

Madison Wong 1G wrote:I was a bit confused on this too. Does increasing the number of photons increase the energy, or does it not affect the energy since changing the intensity of light didn't result in more emitted electrons?

When the intensity of the light increases, the number of photons increases, but this does not affect the energy of the photons. If you want emit more electrons, you would have to use a light source with shorter wavelengths because then the photons will have a higher energy that will be sufficient to emit more electrons.