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I understand the photoelectric effect demonstrates that electrons are only dislodged from a metal if incident light meets a minimum threshold frequency. I wonder if a varying intensity might also contribute to the effect.

If one fixes the frequency of light being shone onto a metal below the threshold frequency, does a rapidly varying intensity cause electrons to be emitted?

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  • $\begingroup$ What do you mean by rapidly varying? $\endgroup$ – Rob Jeffries Mar 26 '15 at 23:20
  • $\begingroup$ By rapidly varying, I mean time varying. I'm asking if time varying intensity contributes to the energy that induces electron emission. $\endgroup$ – Luke Burns Mar 27 '15 at 5:03
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Higher intensity can contribute through secondary effects. As the beam intensity increases, then the likelihood of two photons impinging on an atom (almost) simultaneously also increases. If the two photon energies together are greater than the work function, then ionization can occur even though any single photon would be insufficient to do so.

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  • $\begingroup$ Then let's consider low intensities that vary rapidly. Does time-variance of (low) intensity contribute to the energy of the light and induce electron emission? $\endgroup$ – Luke Burns Mar 26 '15 at 21:14
  • $\begingroup$ I am unaware of such effects. The only information I found similar to that wasn't specific to the photoelectric effect. Perhaps others will have a more definitive answer. $\endgroup$ – BowlOfRed Mar 26 '15 at 21:33
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Time varying intensity means time varying flux of photons. Above threshold this gives a consequent time varying photocurrent at anode. This is the basis of optical sound since the 1920's, where the intensity of light was modulated by the varyng transparency of the soundtrack on the film and then read by a phototube. Below threshold: as already answered, very large intensities on needlelike cathodes can simulate classic behaviour because of multiphoton hits, but this has nothing to do with time variations

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