Main Entry: Planck's constant
Pronunciation: 'pla[ng](k)s-, 'plä[ng](k)s-
Function: noun
: a constant that gives the unvarying ratio of the energy of aquantum of radiation to its frequency and that has an approximate value of 6.626 × 10⁻³⁴ joule second —symbol h
Planck /'plä[ng]k,/ Max Karl Ernst Ludwig (1858–1947), German physicist. Planck is credited with originating the quantum theory in physics. Throughout his career he taughttheoretical physics at a succession of German universities. In 1900 he introduced Planck's constant as a part of his accurate formulation of the distribution of the radiation emitted by a blackbody,which is a perfect absorber of radiant energy. His discoveries established the field of quantum physics. Planck is also remembered for his work relating to thermodynamics and mechanics and toelectrical and optical problems associated with radiation of heat and with the quantum theory. He was awarded the Nobel Prize for Physics in 1918.

Planck's constant (plängks)
n.

Symbol h The constant of proportionality relating the energy of a photon to the frequency of that photon. Its value is approximately 6.626 × 10-³⁴ joule-second.

Planck's constant   (plängks)  Pronunciation Key  A physical constant that is used extensively in quantum mechanics and fixes the scale of quantization of many phenomena, such as the relation between the energy of a photon (a quantum of light) and its wavelength. Its value is approximately 6.626 × 10-34 joule-seconds (equivalent to units of angular momentum). Planck's constant is fundamental to phenomena as the quantization of angular momentum and is used in Heisenberg's Uncertainty Principle. See also Dirac's constant, quantize.