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The Planck constant, or Planck's constant, denoted by , [1] is a fundamental physical constant [1] of foundational importance in quantum mechanics: a photon's energy is equal to its frequency multiplied by the Planck constant, and the wavelength of a matter wave equals the Planck constant divided by the associated particle momentum.
Symbol Quantity Value [a] [b] Relative standard uncertainty Ref [1]; speed of light in vacuum : 299 792 458 m⋅s −1: 0 [2]Planck constant: 6.626 070 15 × 10 −34 J⋅Hz −1: 0 [3]= / reduced Planck constant
reduced Planck constant in eV⋅s ħ = 6.582 119 569... × 10 −16 eV⋅s: u r (ħ) = 0 [12] k: Boltzmann constant: k = 1.380 649 × 10 −23 J⋅K −1: u r (k) = 0 [13] KJ: Josephson constant: K J = 483 597.8484... × 10 9 Hz⋅V −1: u r (K J) = 0 [14] NA: Avogadro constant: N A = 6.022 140 76 × 10 23 mol −1: u r (N A) = 0 ...
This equation is known as the Planck relation. Additionally, using equation f = c/λ, = where E is the photon's energy; λ is the photon's wavelength; c is the speed of light in vacuum; h is the Planck constant; The photon energy at 1 Hz is equal to 6.626 070 15 × 10 −34 J, which is equal to 4.135 667 697 × 10 −15 eV.
In SI units, the values of c, h, e and k B are exact and the values of ε 0 and G in SI units respectively have relative uncertainties of 1.6 × 10 −10 [16] and 2.2 × 10 −5. [17] Hence, the uncertainties in the SI values of the Planck units derive almost entirely from uncertainty in the SI value of G .
Robert A. Millikan and Harvey Fletcher's oil drop experiment first directly measured the magnitude of the elementary charge in 1909, differing from the modern accepted value by just 0.6%. [4] [5] Under assumptions of the then-disputed atomic theory, the elementary charge had also been indirectly inferred to ~3% accuracy from blackbody spectra ...
The Planck relation [1] [2] [3] (referred to as Planck's energy–frequency relation, [4] the Planck–Einstein relation, [5] Planck equation, [6] and Planck formula, [7] though the latter might also refer to Planck's law [8] [9]) is a fundamental equation in quantum mechanics which states that the energy E of a photon, known as photon energy, is proportional to its frequency ν: =.
A fundamental physical constant occurring in quantum mechanics is the Planck constant, h. A common abbreviation is ħ = h /2 π , also known as the reduced Planck constant or Dirac constant . Quantity (common name/s)