Planck's constant

American  

Or Planck constant

noun

Physics.

1. 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 Scientific  

/ plängks /

1. 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.

2. See also Dirac's constant quantize

---

Planck's constant Cultural  

1. 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.

---

Discover More

Knowing Planck's constant sets the scale of energy for events in which the atom and subatomic particles take part.

Etymology

Origin of Planck's constant

First recorded in 1905–10; named after M. K. E. Planck

Example Sentences

The ability to precisely measure resistance comes from von Klitzing’s discovery that resistance is quantized at values that are proportional to a combination of two fundamental physical constants: the charge of the electron and Planck’s constant.

From Nature

The product of the uncertainties in position and momentum has a fundamental minimum set by Planck’s constant.

From Scientific American

For both Planck’s constant and the speed of light, different laboratories have arrived at the same number using different methods — a sign of reproducibility.

From Nature

In the case of Planck’s constant, there’s now enough confidence in its value for it to become the basis of the International System of Units definition of the kilogram that was confirmed last May.

From Nature

That frequency defines the length of a second, which together with the speed of light defines the length of a metre, which in turn, together with knowing Planck’s constant of quantum theory, allows us to calculate what a kilogram is.

From The Guardian