Another Question

To: Tom VanFlandern 04/11/03

 T
hank you for your last reply. I know I'm getting more than my money's worth ... but ... I have another Q.

You stated that ...

... in regard to the photoelectric effect -

"The frequency at which ejection occurs is not due to reaching some threshold, as your description implies, because if the frequency is further increased, the ejection no longer occurs. Instead, ejection occurs only when incident light frequency matches the electrons own intrinsic frequency (or some exact multiple thereof). Ejection behaves like a resonance phenomenon, not a threshold phenomenon."

My description was:

We have photoelectric effect experiments wherein a metal is exposed to light of frequency 'v' such that no electrons are ejected from the metal no matter what the intensity of the incident light at that frequency. Then, when the frequency is raised ... at some point electrons are ejected from the metal ... and ... that emission is dependent on the intensity, i.e. greater intensity equals more electron emission and lesser intensity equals less emission of electrons. And ... the electrons are ejected even if the intensity is reduced to single photons incident on the metal.

This is apparently at odds with experiment as may be seen from the following [from Google "photoelectric effect"] - http://theory.uwinnipeg.ca/physics/quant/node3.html

"When these photons hit the metal, they could give up some or all of their energy to an electron. A certain amount of energy would be required to release the electrons from their bonds to the metal - this energy is called the work function of the metal. The remaining energy would appear as kinetic energy of the released electron."

Comment:
I see nothing "at odds" yet.

And from ...
http://www.cmmp.ucl.ac.uk/~ajf/1B23/qm/node4.html

"This enables the maximum kinetic energy of the emitted electrons to be measured. There are two surprises (Figure 2): (a) if the frequency of light is less than some critical value f0, no electrons are detected;

Comment:
Fully consistent with my description

(b) for higher frequencies, the energy of the most energetic electrons increases steadily with the frequency.

Comment:
This appears contrary to everyday experience in astronomy. See below.

These features are independent of how intense the light is."

One last observation:
If what you say is valid, would a photon at exactly one half of the electron's frequency transfer energy to that electron via resonance?

Comment:
No. The resonant frequencies for hydrogen are those in the Balmer series, followed by those in the Lyman series, etc. For other elements, the resonances are at other frequencies.

For, if so, it would appear to be a clear contradiction of experiment for they state explicitly that photons of energy less than the work function cannot cause the ejection of electrons regardless of intensity.

All the other pages I visited agreed with this and there was even an applet simulation to play with where you could vary the energy of the photon, i.e. by e=hv, change the frequency by non-integral amounts. There is no mention of an integral multiple (of the frequency) requirement nor is any such requirement anywhere implied (and I don't remember ever reading anything about that ;o).

Do you have an http I could check out concerning this aspect of the phenomenon?

Comment:
I have learned not to always trust the Internet as having reliable sources. Too many people who don't know what they are talking about create attractive web sites.

Comment:
In the Einstein description of the photoelectric effect, the arriving photon is completely absorbed by the surface it impinges upon. This can only happen at certain critical frequencies corresponding to the spectral lines of the substance or substances in the surface. It cannot happen at non-spectral-line frequencies, whether lower or higher.

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