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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.
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.
The constants listed here are known values of physical constants expressed in SI units; that is, physical quantities that are generally believed to be universal in nature and thus are independent of the unit system in which they are measured. Many of these are redundant, in the sense that they obey a known relationship with other physical ...
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 ...
In particle physics and physical cosmology, the Planck scale is an energy scale around 1.22 × 10 28 eV (the Planck energy, corresponding to the energy equivalent of the Planck mass, 2.176 45 × 10 −8 kg) at which quantum effects of gravity become significant.
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: =.
The conductance quantum, denoted by the symbol G 0, is the quantized unit of electrical conductance.It is defined by the elementary charge e and Planck constant h as: = = = 7.748 091 729... × 10 −5 S.
As such, the fine-structure constant is just a quantity determining (or determined by) the elementary charge: e = √ 4πα ≈ 0.302 822 12 in terms of such a natural unit of charge. In the system of atomic units , which sets e = m e = ħ = 4 πε 0 = 1 , the expression for the fine-structure constant becomes α = 1 c . {\displaystyle \alpha ...