How has the quantum concept appeared?

Trying to write the correct formula of thermal radiation…

At the end of the XIX century, the dependence of the thermal-radiation energy upon body’s temperature was being described by the Rayleigh-Jeans formula that, however, was not consistent with experiments for the blue light and led to the “ultraviolet catastrophe” — an infinitely high energy of radiation — for shorter wavelengths of light. While working on this problem and based on the previous achievements of Ludwig Boltzmann, Max Planck has obtained a formula that describes the radiation correctly. It contains a constant coefficient that determines a minimal energy (a quantum) of light of a given wavelength, which has been later named after the physicist. At that time, a lot of attention has been paid to radiation of heated bodies in physics. The corresponding basic researches were supported by the practical necessity due to the proliferation of light bulbs.

The quantum formula for spectrum of thermal radiation obtained by Planck

Planck, as well as Dirac later on, has come to the surprising discovery while working out a formula.


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