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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.
For example, in Stoney units, the elementary charge is set to e = 1 while the reduced Planck constant is subject to measurement, ħ ≈ 137.03, and in Planck units, the reduced Planck constant is set to ħ = 1, while the elementary charge is subject to measurement, e ≈ (137.03) 1/2.
The Planck time, denoted t P, is defined as: = = This is the time required for light to travel a distance of 1 Planck length in vacuum, which is a time interval of approximately 5.39 × 10 −44 s. No current physical theory can describe timescales shorter than the Planck time, such as the earliest events after the Big Bang. [ 30 ]
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)
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.
h_eV/Hz: Planck constant in eV/Hz h = 4.135 667 696... × 10 −15 eV⋅Hz −1: u r (h) = 0 [10] hbar: reduced Planck constant: ħ = 1.054 571 817... × 10 −34 J⋅s: u r (ħ) = 0 [11] hbar_eVs: 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 × ...
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: =.
As a result of the 2019 revision of the SI, the Planck constant h has a fixed value h = 6.626 070 15 × 10 −34 J⋅Hz −1, [13] which, together with the definitions of the second and the metre, provides the official definition of the kilogram. Furthermore, the elementary charge also has a fixed value of e = 1.602 176 634 × 10 −19 C ...