Post Module #17  [ENDORSED]

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Post Module #17

Postby tiffanyteguh1C » Tue Oct 17, 2017 3:13 am

I'm stuck on this conceptual question from the photoelectric effect post-assessment:
If long wavelength light is not ejecting electrons from a metal surface will increasing the intensity of the light result in electrons being ejected? Justify your answer.

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Re: Post Module #17

Postby Maria1E » Tue Oct 17, 2017 1:58 pm

It will not; that is what the scientists performing this experiment found surprising. If light had only wave properties then increasing the intensity should have resulted in the ejection of electrons, but it didn't. The conclusion of the experiment was that light is made of photons, or individual packets of energy. If each individual photon doesn't have enough energy to eject an electron then increasing the intensity, or amount of photons, will have no effect. Basically, light was not acting like a classical wave in the photoelectric experiment. Light sources with a long wavelength could not eject electrons even with high intensity light. If the wavelength was short enough, electrons would always be ejected, even if the intensity of the light was low. In order to eject electrons, one would need to make the wavelength shorter rather than make the intensity higher.

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Re: Post Module #17  [ENDORSED]

Postby Amelia Georgius 1K » Sun Oct 22, 2017 11:05 pm

Increasing the intensity of the light, the amplitude of the wave, would not eject electrons, which showed that light had particle like properties because they were just increasing the number of photons rather than increasing their energy. If more photons were shone onto the metal with the same energy then no electrons would be emitted because none of the photons would be strong enough to emit any electrons. Increasing the energy of the photons would cause electrons to be emitted.

Aliza Ajmal 1D
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Re: Post Module #17

Postby Aliza Ajmal 1D » Mon Nov 06, 2017 12:00 am

Just like the above two posts, remember that one photon will eject one electron. This photon must have enough energy to eject the electron (energy must be greater than or equal to the work function). Increasing intensity refers to increasing the number of photons. If you add more photons that are weak, and only one photon ejects one electron, a singular weak photon cannot kick off the electron from the metal. In class, Dr. Lavelle used the example of a bunch of students not being able to jump over a hurdle. If the students can't jump over the hurdle, then adding more useless weak students (lol) wouldn't lead to more people being able to jump over the hurdle. Hope this helps, and this example can help you visualize this concept!

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