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Photon energy can be expressed using any energy unit. Among the units commonly used to denote photon energy are the electronvolt (eV) and the joule (as well as its multiples, such as the microjoule). As one joule equals 6.24 × 10 18 eV, the larger units may be more useful in denoting the energy of photons with higher frequency and higher ...
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 particle of mass m has a rest energy of E = mc 2. The Compton wavelength for this particle is the wavelength of a photon of the same energy. For photons of frequency f, energy is given by = = =, which yields the Compton wavelength formula if solved for λ.
In some cases, two energy transitions can be coupled so that, as one system absorbs a photon, another nearby system "steals" its energy and re-emits a photon of a different frequency. This is the basis of fluorescence resonance energy transfer, a technique that is used in molecular biology to study the interaction of suitable proteins. [123]
According to Planck's distribution law, the spectral energy density (energy per unit volume per unit frequency) at given temperature is given by: [4] [5] (,) = alternatively, the law can be expressed for the spectral radiance of a body for frequency ν at absolute temperature T given as: [6] [7] [8] (,) = where k B is the Boltzmann ...
A frequency (or spectral energy) emitted in a transition from n 1 to n 2 therefore represents the photon energy emitted or absorbed when an electron makes a jump from orbital 1 to orbital 2. Later models found that the values for n 1 and n 2 corresponded to the principal quantum numbers of the two orbitals.
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.
The dimensionless quantity = / expresses the energy of the incident photon in terms of the electron rest energy (~511 keV), and may also be expressed as = /, where = / is the Compton wavelength of the electron (~2.42 pm).