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In the study of heat transfer, Schwarzschild's equation[1][2][3] is used to calculate radiative transfer (energy transfer via electromagnetic radiation) through a medium in local thermodynamic equilibrium that both absorbs and emits radiation. The incremental change in spectral intensity, [4] (dIλ, [W/sr/m 2 /μm]) at a given wavelength as ...
Fick's first law relates the diffusive flux to the gradient of the concentration. It postulates that the flux goes from regions of high concentration to regions of low concentration, with a magnitude that is proportional to the concentration gradient (spatial derivative), or in simplistic terms the concept that a solute will move from a region of high concentration to a region of low ...
Spectral flux density. In spectroscopy, spectral flux density is the quantity that describes the rate at which energy is transferred by electromagnetic radiation through a real or virtual surface, per unit surface area and per unit wavelength (or, equivalently, per unit frequency). It is a radiometric rather than a photometric measure.
CGS units. 10−23 erg⋅s−1⋅cm−2⋅Hz−1. The jansky (symbol Jy, plural janskys) is a non- SI unit of spectral flux density, [1] or spectral irradiance, used especially in radio astronomy. It is equivalent to 10 −26 watts per square metre per hertz. The flux density or monochromatic flux, S, of a source is the integral of the spectral ...
Radiative flux. Radiative flux, also known as radiative flux density or radiation flux (or sometimes power flux density[1]), is the amount of power radiated through a given area, in the form of photons or other elementary particles, typically measured in W/m 2. [2] It is used in astronomy to determine the magnitude and spectral class of a star ...
v. t. e. In quantum mechanics, the probability current (sometimes called probability flux) is a mathematical quantity describing the flow of probability. Specifically, if one thinks of probability as a heterogeneous fluid, then the probability current is the rate of flow of this fluid. It is a real vector that changes with space and time.
M⋅L −1 ⋅T −3: Irradiance Flux density: E e [nb 5] watt per square metre W/m 2: M⋅T −3: Radiant flux received by a surface per unit area. This is sometimes also confusingly called "intensity". Spectral irradiance Spectral flux density: E e,ν [nb 6] watt per square metre per hertz W⋅m −2 ⋅Hz −1: M⋅T −2: Irradiance of a ...
Noise-equivalent flux density. In optics the noise-equivalent flux density (NEFD) or noise-equivalent irradiance (NEI) of a system is the level of flux density required to be equivalent to the noise present in the system. [1] It is a measure used by astronomers in determining the accuracy of observations.