Planck’s constant defines the boundary between the macrocosm, where the laws of Newtonian mechanics operate, and the microcosm, where the laws of quantum mechanics operate.

Max Planck – one of the founders of quantum mechanics – came to the ideas of quantizing energy, trying to theoretically explain the process of interaction between recently discovered electromagnetic waves (cm. Maxwell’s equations) and atoms and, thus, solve the problem of blackbody radiation. He realized that to explain the observed emission spectrum of atoms, one must take for granted that atoms emit and absorb energy in portions (which the scientist called quanta) and only at individual wave frequencies. The energy carried by one quantum is equal to:


E = hv

Where v Is the radiation frequency, and helementary quantum of action, which is a new universal constant, which soon received the name Planck’s constant… Planck was the first to calculate its value based on experimental data h = 6,548 × 10–34 J s (in SI system); according to modern data h = 6,626 × 10–34 J s. Accordingly, any atom can emit a wide range of interconnected discrete frequencies, which depends on the orbits of the electrons in the atom. Soon, Niels Bohr will create a coherent, albeit simplified, model of the Bohr atom, consistent with the Planck distribution.

Having published his results at the end of 1900, Planck himself – and this is evident from his publications – at first did not believe that quanta are a physical reality, and not a convenient mathematical model. However, when five years later, Albert Einstein published an article explaining the photoelectric effect based on energy quantization radiation, in scientific circles Planck’s formula began to be perceived not as a theoretical game, but as a description of a real physical phenomenon at the subatomic level, proving the quantum nature of energy.

Planck’s constant appears in all equations and formulas of quantum mechanics. It, in particular, determines the scale from which the Heisenberg uncertainty principle comes into force. Roughly speaking, Planck’s constant indicates to us the lower limit of spatial quantities, after which quantum effects cannot be ignored. For grains of sand, say, the uncertainty in the product of their linear size and speed is so insignificant that it can be neglected. In other words, Planck’s constant draws the border between the macrocosm, where the laws of Newtonian mechanics operate, and the microcosm, where the laws of quantum mechanics come into force. Having been obtained only for the theoretical description of a single physical phenomenon, Planck’s constant soon became one of the fundamental constants of theoretical physics, determined by the very nature of the universe.

See also:
Spectroscopy
Photoelectric effect
Max Karl Ernst Ludwig PLANK
Max Karl Ernst Ludwig PLANK
Max Karl Ernst Ludwig Plank, 1858-1947

German physicist. Born in Kiel in the family of a professor of jurisprudence. As a virtuoso pianist, in his youth, Planck was forced to make a difficult choice between science and music (it is said that before the First World War, at his leisure, pianist Max Planck often composed a very professional classical duet with violinist Albert Einstein – Approx. translator) Planck defended his doctoral dissertation on the second law of thermodynamics in 1889 at the University of Munich – and in the same year became a teacher, and from 1892 – a professor at the University of Berlin, where he worked until his retirement in 1928. Planck is rightfully considered one of the fathers of quantum mechanics. Today, a whole network of German research institutes bears his name.

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