The recent posts on the photoelectric effect exhibits Planck's constant h as a conversion standard between the units of light frequency \nu in Hz\, = 1/s as periods per second and electronvolt (eV), expressed in Einstein's law of photoelectricity:
- h\times (\nu -\nu_0) = eU,
where \nu_0 is smallest frequency producing a photoelectric current, e is the charge of an electron and U the stopping potential in Volts V for which the current is brought to zero for \nu > \nu_0. Einstein obtained, referring to Lenard's 1902 experiment with \nu -\nu_0 = 1.03\times 10^{15}\, Hz corresponding to the ultraviolet limit of the solar spectrum and U = 4.3\, V
- h = 4.17\times 10^{-15} eVs
to be compared with the reference value 4.135667516(91)\times 10^{-15}\, eV used in Planck's radiation law. We see that here h occurs as a conversion standard between Hertz Hz and electronvolt eV with
- 1\, Hz = 4.17\times 10^{-15}\, eV
To connect to quantum mechanics, we recall that Schrödinger's equation is normalized with h so that the first ionization energy of Hydrogen at frequency \nu = 3.3\times 10^{15}\, Hz equals 13.6\, eV, to be compared with 3.3\times 4.17 = 13.76\, eV corresponding to Lenard's photoelectric experiment.
We understand that Planck's constant h can be seen as a conversion standard between light energy measured by frequency and electron energy measured in electronvolts. The value of h can then be determined by photoelectricity and thereafter calibrated into Schrödinger's equation to fit with ionization energies as well as into Planck's law as a parameter in the high-frequency cut-off (without a very precise value). The universal character of h as a smallest unit of action is then revealed to simply be a human convention standard without physical meaning. What a disappointment!
This fits with the article Quantum Theory without Planck's Constant ny John P. Ralston:
- Planck's constant was introduced as a fundamental scale in the early history of quantum mechanics. We find a modern approach where Planck's constant is absent: it is unobservable except as a constant of human convention.
Finally: It is natural to view frequency \nu as a measure of energy per wavelength, since radiance as energy per unit of time scales with \nu\times\nu in accordance with Planck's law, which can be viewed as \nu wavelengths each of energy \nu passing a specific location per unit of time. We thus expect to find a linear relation between frequency and electronvolt as two energy scales: If 1 € (Euro) is equal to 9 Skr (Swedish Crowns), then 10 € is equal to 90 Skr.