Search results
Results from the WOW.Com Content Network
The Bekenstein–Hawking entropy of a black hole is one-fourth the area of its event horizon in units of Planck length squared. [11]: 370 Since the 1950s, it has been conjectured that quantum fluctuations of the spacetime metric might make the familiar notion of distance inapplicable below the Planck length.
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: =.
In physics, Planck's law (also Planck radiation law [1]: 1305 ) describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature T, when there is no net flow of matter or energy between the body and its environment.
Using the values known in 2018 and Planck units for Ω Λ = 0.6889 ± 0.0056 and the Hubble constant H 0 = 67.66 ± 0.42 (km/s)/Mpc = (2.192 7664 ± 0.0136) × 10 −18 s −1, Λ has the value of = = = where is the Planck length. A positive vacuum energy density resulting from a cosmological constant implies a negative pressure, and vice versa.
Planck considered only the units based on the universal constants G, h, c, and k B to arrive at natural units for length, time, mass, and temperature, but no electromagnetic units. [7] The Planck system of units is now understood to use the reduced Planck constant, ħ, in place of the Planck constant, h. [8]
since / = 1.239 841 984... × 10 −6 eV⋅m [4] where h is the Planck constant, c is the speed of light, and e is the elementary charge. The photon energy of near infrared radiation at 1 μm wavelength is approximately 1.2398 eV.
In theories of particle physics based on string theory, the characteristic length scale of strings is assumed to be on the order of the Planck length, or 10 −35 meters, the scale at which the effects of quantum gravity are believed to become significant. [15]
Compton wavelength. The Compton wavelength is a quantum mechanical property of a particle, defined as the wavelength of a photon whose energy is the same as the rest energy of that particle (see mass–energy equivalence). It was introduced by Arthur Compton in 1923 in his explanation of the scattering of photons by electrons (a process known ...