On December 14, 1900, Plack published his findings on Quantum theory in the German Physical Society.
His study on black-body radiation shows that the radiation is consists of quanta with a specific energy.
Planck’s first derivation of the famous Planck black-body radiation law was published in 1901.
Reference Sources:
[1] The Nobel Prize in Physics 1918. NobelPrize.org. Published 2021. Accessed December 15, 2021. https://www.nobelprize.org/prizes/physics/1918/planck/facts/
[2] Wikipedia Contributors. Quantum. Wikipedia. Published December 12, 2021. Accessed December 15, 2021. https://en.wikipedia.org/wiki/Quantum.
[3] On This Day – Dec 14 : Max Planck quantum theory. RSC Education. Published 2012. Accessed December 15, 2021. https://edu.rsc.org/resources/on-this-day-dec-14—max-planck-quantum-theory/11214.article
[4] Max Planck: the reluctant revolutionary – Physics World. Physics World. Published December 2000. Accessed December 15, 2021. https://physicsworld.com/a/max-planck-the-reluctant-revolutionary/.