Incorrect interpretation of the photoelectric effects

[worlov]

Only an excuse...

[worlov]

Another picture from http://www.cobalt.chem.ucalgary.ca/ziegler/educmat/chm386/rudiment/tourexp/photelec.htm

 

"This graph shows the typical results of an experiment. For a given light frequency and a particular metal for the cathode, the photocurrent is constant until a large enough retarding potential prevents the ejected electrons from reaching the anode. This potential is called the stopping potential and just matches the kinetic energy of the ejected electrons. When a higher energy light source is used (greater frequency, shorter wavelength), the ejected electrons possess a greater kinetic energy and so the stopping potential is correspondingly larger."

 

The text is not completely. It should be emphasized that the intensity of light is constant, otherwise, these curves have no sense. For modifying intensity is presented other graph:

 

Here, however, stressed that the wavelength remains constant:

 

"This graph shows how the photocurrent increases when the light intensity increases but the wavelength is held constant. The stopping potential is the same however, suggesting that the kinetic energy of the ejected electrons is the same and hence independent of light intensity. This is the opposite of what would be expected classically."

 

 

 

 

 

 

 

[csmyth3025]

Physicists have studied Einstein's interpretation of the photoelectric effect for over 90 years. They have subsquently taught their students this interpretation. Presumably these teachers are confident that they understand the logic and experimental evidence supporting this theory.

 

How is it, do you suppose, that you're the first person to discover that this interpretation is wrong? Do you feel that no one else has been smart enough to realize that Einstein's interpretation is wrong? Or, perhaps, do you think that the scientific community has just been turning a blind eye to Einstein's mistake all these years?

 

Chris

[swansont]

Another picture from http://www.cobalt.chem.ucalgary.ca/ziegler/educmat/chm386/rudiment/tourexp/photelec.htm

 

"This graph shows the typical results of an experiment. For a given light frequency and a particular metal for the cathode, the photocurrent is constant until a large enough retarding potential prevents the ejected electrons from reaching the anode. This potential is called the stopping potential and just matches the kinetic energy of the ejected electrons. When a higher energy light source is used (greater frequency, shorter wavelength), the ejected electrons possess a greater kinetic energy and so the stopping potential is correspondingly larger."

 

The text is not completely. It should be emphasized that the intensity of light is constant, otherwise, these curves have no sense. For modifying intensity is presented other graph:

 

Here, however, stressed that the wavelength remains constant:

 

"This graph shows how the photocurrent increases when the light intensity increases but the wavelength is held constant. The stopping potential is the same however, suggesting that the kinetic energy of the ejected electrons is the same and hence independent of light intensity. This is the opposite of what would be expected classically."

 

IOW, the text does not address in any way the objection that you have. Maybe because it's a triviality that the number of photons goes down as you increase frequency at constant power, and that's not a concept one wishes to explore when studying the photoelectric effect; it would be a distraction from the much more important results.

 

You are manufacturing a problem that doesn't actually exist on its own.

[worlov]

How is it, do you suppose, that you're the first person to discover that this interpretation is wrong? Do you feel that no one else has been smart enough to realize that Einstein's interpretation is wrong? Or, perhaps, do you think that the scientific community has just been turning a blind eye to Einstein's mistake all these years?

 

I would answer with "Yes " your last question. Because the scientists always avoid to mention the relationship I = const, v - variable and i = const. But it is no less important as the relationship between the frequency of light and kinetic energy of electrons. Here Einstein's photon hypothesis fails!

[Klaynos]

Until saturation increasing the intensity (flux of photons) WILL increase the photo current.

 

BUT only if the photon energy is above the work function of the metal. If the photon energy is below the work function then increasing the intensity will continue to result in no photo emitted photons. With the given that we're ignoring multi-photon emission, which requires very very very high fields and is a severely non-linear process. I'm working on a paper currently where we exploit multi-photon electro emission but we are hitting our samples with energy densities of around up to around 90GW/cm² If we try to go higher our samples go bye bye...

[worlov]

IOW, the text does not address in any way the objection that you have. Maybe because it's a triviality that the number of photons goes down as you increase frequency at constant power, and that's not a concept one wishes to explore when studying the photoelectric effect; it would be a distraction from the much more important results.

 

You are manufacturing a problem that doesn't actually exist on its own.

 

An honest man would now prefer to admit that Mr. Einstein was wrong

[Klaynos]

An honest man would now prefer to admit that Mr. Einstein was wrong

 

It seems that you just have a slight understanding...

 

It also seems like your knowledge on the matter is built up from googling, that is not a great way to learn physics.

[swansont]

An honest man would now prefer to admit that Mr. Einstein was wrong

 

I think that one might realize that holding Einstein to the use of I=nh[math]\nu[/math] for intensity (or, rather, total power, since Intensity as it is now defined is per unit area) is unreasonable, since that definition didn't frikkin' exist when he wrote the paper. He's citing Lenard's work from 1902. Nobody knew that light were quanta and that their energy depended on frequency when he did the investigation. Intensity could not have been defined the way you are using it, thus you have not shown Einstein to be wrong. You're nitpicking about terminology that was still under development at the time.

Edited April 21, 2011 by swansont
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[worlov]

It seems that you just have a slight understanding...

 

What has "very very very high fields" with simple linear photoelectric effect?

[Klaynos]

What has "very very very high fields" with simple linear photoelectric effect?

 

Nothing, which is why I said we were ignoring that. My explanation above agrees with both your graphs and the excepted understanding and experimental evidence of the photoelectric effect.

[worlov]

Nothing, which is why I said we were ignoring that. My explanation above agrees with both your graphs and the excepted understanding and experimental evidence of the photoelectric effect.

 

I can read it anywhere. This is nothing new. But what I say is new.

 

...You're nitpicking about terminology that was still under development at the time.

 

By intensity of light I mean generally accepted concept.

Edited April 21, 2011 by worlov