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is energy (joules in the SI system) [2] is the Planck constant; is frequency [2] 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
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 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.
where ν is the frequency of the wave, λ is the wavelength, ω = 2πν is the angular frequency of the wave, and v p is the phase velocity of the wave. The dependence of the wavenumber on the frequency (or more commonly the frequency on the wavenumber) is known as a dispersion relation.
These equations have the same form as Maxwell's equations (and the Lorentz force equation) of electromagnetism, with mass density replacing charge density, and with 1 / 4 π G replacing ε 0. Normalizes the characteristic impedance Z g of gravitational radiation in free space to 1 (normally expressed as 4 π G / c ).
Radiant exitance of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅m −2 ⋅nm −1. "Spectral emittance" is an old term for this quantity. This is sometimes also confusingly called "spectral intensity". M e,λ [nb 4] watt per square metre, per metre W/m 3: M⋅L −1 ⋅T −3: Radiant exposure: H e: joule ...
In spectroscopy, the unit cm −1 ≈ 0.000 123 9842 eV is used to represent energy since energy is inversely proportional to wavelength from the equation = = /. In discussions of energy production and consumption, the units barrel of oil equivalent and ton of oil equivalent are often used.
List of orders of magnitude for energy; Factor (joules) SI prefix Value Item 10 −34: 6.626 × 10 −34 J: Energy of a photon with a frequency of 1 hertz. [1]8 × 10 −34 J: Average kinetic energy of translational motion of a molecule at the lowest temperature reached (38 picokelvin [2] as of 2021)