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Planck's constant
or Planck constant
noun
, Physics.
- the fundamental constant of quantum mechanics, expressing the ratio of the energy of one quantum of radiation to the frequency of the radiation and approximately equal to 6.624 × 10− 27 erg-seconds. : h
Planck's constant
/ plängks /
- 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
Planck's constant
- A universal constant , first discovered by Max Planck , that states the mathematical relationship between the frequency of an electromagnetic wave and the energy in that wave. Planck's discovery unifies the seemingly contradictory observations that energy sometimes acts like a wave and at other times acts as if it is made up of particles.
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Notes
Knowing Planck's constant sets the scale of energy for events in which the atom and subatomic particles take part.
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Word History and Origins
Origin of Planck's constant1
First recorded in 1905–10; named after M. K. E. Planck
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