Planck's constant

== English == === Etymology === Named for Max Planck (1858–1947), German theoretical physicist, who discovered it in 1900. === Pronunciation === === Proper noun === Planck's constant (quantum mechanics) the constant of proportionality (symbol ℎ), relating the energy and frequency of a photon (6.626×10−34 joule-second); also related to the indeterminacy limit in the Heisenberg uncertainty principle; the quantum of action ==== Translations ====