Photoelectric and summation of photons energy

[hokhani]

TL;DR

Why the photon energies don't get summed?

Classical electromagnetic field can't explain photoelectric effect since at any frequency, increasing the intensity only increases the photon number and don't increase the wave amplitude (as was thought in classical waves). Since photons don't have enough energy they can not excite electrons.
Here, I know that one photon can not excite an electron but how about a large number of photons radiating on one electron?

 

[PeroK]

There is no such thing as a photon in classical EM.

It's not just that the frequency of the light is the key factor. The dislocated electrons have a precise kinetic energy for each frequency. Where the KE is the difference between the photon energy (for a given frequency) and the energy to release the electron.

In the classical model, even if the electrons could be released by wave intensity, the KE would not be a precise value for a given frequency. The KE should depend on the intensity.

Both these factors (threshold energy and KE) show that the energy imparted to an electron depends only on the frequency of the light and not its intensity. This is not consistent with a classical wave model.

 

[hokhani]

show that the energy imparted to an electron depends only on the frequency of the light and not its intensity.

If I understood correctly, you mean that intensity is independent of frequency. Isn't it?

 

[PeroK]

If I understood correctly, you mean that intensity is independent of frequency. Isn't it?

Intensity is the amount of power per unit area.

Frequency in classical EM relates to the speed of oscillation of the electric and magentic fields. And, is inversely proportional to wavelength. There is no direct correlation between the intensity and frequency/wavelength.

 

[weirdoguy]

Classical electromagnetic field can't explain photoelectric effect

As far as I know, proper quantum mechanical explanation does not require EM field to be quantum. It requires electrons to be quantum, EM field can be treated classicaly. I know everyone is hung up on Einsteins explanation from 1905, but it was (by his own words) heuristic and things moved on since then. @vanhees wrote an insight where he briefly discussed this issue.

 

[hokhani]

@vanhees wrote an insight where he briefly discussed this issue.

Could you please send the link to this insight?

 

[weirdoguy]

https://www.physicsforums.com/insights/sins-physics-didactics/

 

[hokhani]

It's not just that the frequency of the light is the key factor.

As far as I know, photoelectric field requires a threshold frequency that under this frequency the effect can't be observed.

 

[JimWhoKnew]

Here, I know that one photon can not excite an electron but how about a large number of photons radiating on one electron?

Several photons below the frequency threshold may extract an electron from metal (or excite it). It is called "multiphoton absorption" (you can look it up). This effect should be detectable if the experiment setup is sufficiently sensitive.