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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.
Near thermodynamic equilibrium, the emitted radiation is closely described by Planck's law and because of its dependence on temperature, Planck radiation is said to be thermal radiation, such that the higher the temperature of a body the more radiation it emits at every wavelength. Planck radiation has a maximum intensity at a wavelength that ...
120 μm – the geometric mean of the Planck length and the diameter of the observable universe: √ 8.8 × 10 26 m × 1.6 × 10 −35 m; 120 μm – diameter of a human ovum; 170 μm – length of the largest mammalian sperm cell (rat) [102] 170 μm – length of the largest sperm cell in nature, belonging to the Drosophila bifurca fruit fly ...
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: =.
Wavelength is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. [3] [4] The inverse of the wavelength is called the spatial frequency. Wavelength is commonly designated by the Greek letter lambda (λ). For a modulated wave, wavelength may refer to the carrier wavelength of the signal.
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.
The de Broglie wavelength is the wavelength, λ, associated with a particle with momentum p through the Planck constant, h: =. Wave-like behavior of matter has been experimentally demonstrated, first for electrons in 1927 and for other elementary particles, neutral atoms and molecules in the years since.
In 1900, Max Planck postulated the proportionality between the frequency of a photon and its energy , =, [11] [12] and in 1916 the corresponding relation between a photon's momentum and wavelength, =, [13] where is the Planck constant.