Photoelectric effect question

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Discussion Overview

The discussion revolves around the photoelectric effect, specifically addressing the relationship between light intensity, threshold frequency, and the work function of materials. Participants explore theoretical implications and nuances related to the absorption of photons and the conditions under which electrons are emitted from materials.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • One participant questions whether increasing the intensity of light lowers the threshold frequency needed for electrons to be knocked off, while another asserts that it is independent of intensity.
  • A participant reflects on their theory being challenged by the assertion that intensity does not affect threshold frequency.
  • Another participant introduces the idea that high intensity could increase the temperature of the material, suggesting that the work function may depend on temperature, although they acknowledge this might be a minor point.
  • It is noted that increasing light intensity results in more photons, but without sufficient frequency, photons will be reflected rather than absorbed, thus not contributing to heating the material.
  • A participant expresses uncertainty about their knowledge of thermodynamics while discussing the photoelectric effect.
  • One participant raises the possibility that other factors, such as lattice vibrations (phonons), could also absorb photons, questioning the assumption that only electrons are involved in the absorption process.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between light intensity, threshold frequency, and the work function. There is no consensus on whether increasing intensity affects these parameters, and the discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants acknowledge the complexity of the photoelectric effect and its dependence on various factors, including the wavelength of light and the material properties. There are unresolved questions regarding the influence of temperature on the work function and the role of phonons in photon absorption.

hurricane89
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does increasing the intensity of the light lower the threshold frequency at which photons knock off electrons?
 
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No, it's independent of the intensity.
 
so much for my theory then hah. thanks
 
What about an intensity high enough to increase the temperature of the material? The work function is a function of temperature right? Of course I'm nitpicking a little bit but I'm interested :) Of course the material will have to absorb that wavelength.

Edit bad grammar!: I think the proof behind the photoelectric effect was the fact that by increasing the intensity of the of the light impinging on a material there was no change in the work function. Only by changing the wavelength and thus the energy of the light hitting the material changed whether or not electrons were knocked out of the material. Pretty sure that is the basis for the photoelectric affect and the discovery of quantized energy levels. I'm sure someone can correct me if I'm wrong.
 
Last edited:
The work function is a function of temperature right? Of course I'm nitpicking a little bit but I'm interested :) Of course the material will have to absorb that wavelength.

Without the sufficient frequency (small enough wavelength) the photons will be just reflected and not absorbed. There are only two possibilities, one photon of sufficient frequency (hence sufficient energy opposing the work function) is absorbed to knock one electron off the metal, or the photon being knocked off (reflected from the metal).

Higher intensity means that there are more photons in the stream of light, but without the sufficient frequency, they are all going to be reflected, and not increasing the temperature of the metal because no energy is absorbed by the metal to be converted to heat energy.

(I have sufficient knowledge in photoelectric effect, but I'm not very advanced at thermodynamics, so my answer might be wrong).
 
But that's only if electrons are the only thing absorbing the photons. What about the lattice, ie phonons, absorbing the photons? Isn't that why the absorption of a material vs wavelength isn't a flat drop off at the work function? (which you'd expect if the photoelectric effect was the only thing happening).
 

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