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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 ...
Thus Kirchhoff's law of thermal radiation can be stated: For any material at all, radiating and absorbing in thermodynamic equilibrium at any given temperature T, for every wavelength λ, the ratio of emissive power to absorptive ratio has one universal value, which is characteristic of a perfect black body, and is an emissive power which we ...
Radiation constant may refer to: The first and second radiation constants c 1 and c 2 – see Planck's Law; The radiation density constant a – see Stefan ...
If set to yes, the value is preceded by the symbol of the constant, followed by ≈ or = depending on whether round is set. round If omitted, the value is shown along with its standard uncertainty. If set to an integer n, the value is rounded to the first n digits after the decimal point. unit
The Planck constant is fixed at = 6.626 070 15 × 10 −34 J⋅Hz −1 [5] as part of the definition of the SI units. [33] This value is used to define the SI unit of mass, the kilogram: "the kilogram [...] is defined by taking the fixed numerical value of h to be 6.626 070 15 × 10 −34 when expressed in the unit J⋅s, which is equal to ...
Ionizing radiation energy absorbed per unit mass gray (Gy = J/kg) L 2 T −2: Radiance: L: Power of emitted electromagnetic radiation per unit solid angle per emitting source area W/(m 2 ⋅sr) M T −3: Radiant intensity: I: Power of emitted electromagnetic radiation per unit solid angle W/sr L 2 M T −3: scalar Reaction rate: r: Rate of a ...
The fine-structure constant α is the best known dimensionless fundamental physical constant. It is the value of the elementary charge squared expressed in Planck units. This value has become a standard example when discussing the derivability or non-derivability of physical constants.
Definition In SI base units In other SI units SI: Physics: Basic: second [n 1] s: T: time: The duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom. s: SI: Physics: Basic: metre: m: L: length: The distance travelled by light in vacuum in ...