Quantum Mechanics


Hypothesis of "quanta", introduced by Planck, was found useful by Einstein for explanation of the photoelectric effect and for studies of hydrogen spectra. Almost, almost, without Wave Mechanics


The begining of Modern Physics is usually attributed to the lecture of Max Planck done on December 14th, 1900 (and on October 19th, 1900) at the meeting of German Physical Society [1]. In these lectures he formulated the hypothesis that light brings energy in packets (he called them "Energieelement").

Planck did not use the term “quant”, althrough he knew this word, what is clear from his article just next page after the work [1]. Even in 1913 on the “Solvay” Congress he continued to insist that "photon" is a wrong hipothesis.

At that time, Wave Mechanics was still to be formulated: first by deBroglie's hypothesis, then in Schrödinger equation, Dirac's equation and so on.

But just the merely idea of quantisation of physical variables allowed Niels Bohr to construct his model of Hydrogen atom, Einstein to predict laser, Pauli to explain Mendeleev table and so on.




[1] M. Planck, Ueber das Gesetz der Energieverteilung im Normalspektrum, Ann. der Physik IV, 4 (1900) 553



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