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Re: [Phys-L] Photoelectric effect: electron current vs. frequency

I've received requests for copies of the TPT article about a common mistake
in the description of the photoelectric effect.
I want to add some additional commentary that I have taken directly from
this article:

In almost all popular texts that we all use, the I-V plot for the
photoelectric effect shows the dependence of photocurrent and the stopping
potential with the frequency light. This same I-V plot also shows a
saturation level of the photocurrent to one single constant value. And this
saturation value is said to be the same value for all frequencies of light
sources at equal intensity.

But this is wrong.
And this wrong fact is customarily accompanied with the common comment that
the stopping potential does not depend on the * intensity *of the light.

However, concluding that the saturation photocurrent is the same value for
all light sources with the same intensity is itself a contradiction to the
whole point of the PhotoElectric Effect experiment; The saturation level of
the photocurrent depends on the frequency of the light.

The following is partial list of some popular texts that all have the same
wrong figure and the same incorrect related text explanation:

Paul A. Tipler and Ralph A. Llewellyn, Modern Physics, 6th ed. (W. H.
Freeman and Company, New York, 2012), Fig. 3.9;

Hugh D. Young and Roger A. Freedman, Sears and Zemansky’s University
Physics with Modern Physics, Vol. 2, 12th ed. (Pearson, 2008), Fig. 38.5;

Stephen T. Thornton and Andrew Rex, Modern Physics for Scientists and
Engineers, 4th ed. (Brooks/Cole, Boston, 2013), Fig. 3.13;

Arthur Beiser, Concepts of Modern Physics, 6th ed. (McGraw-Hill, New York,
2003), Fig. 2.11;

R. Knight, Physics for Scientists and Engineers (Pearson, San Francisco,
2004), Fig. 38.3; note that this mistake is corrected in later editions of

- Jerry

Gerald Zani
Senior Engineering Technician
Brown University School of Engineering
(401) 863-9571