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The Fraunhofer distance, named after Joseph von Fraunhofer, is the value of: d = 2 D 2 λ , {\displaystyle d={{2D^{2}} \over {\lambda }},} where D is the largest dimension of the radiator (in the case of a magnetic loop antenna , the diameter ) and λ {\displaystyle {\lambda }} is the wavelength of the radio wave .
Rayleigh distance in optics is the axial distance from a radiating aperture to a point at which the path difference between the axial ray and an edge ray is λ / 4. An approximation of the Rayleigh Distance is Z = D 2 2 λ {\displaystyle Z={\frac {D^{2}}{2\lambda }}} , in which Z is the Rayleigh distance, D is the aperture of radiation, λ the ...
The Robinson–Foulds or symmetric difference metric, often abbreviated as the RF distance, is a simple way to calculate the distance between phylogenetic trees. [1]It is defined as (A + B) where A is the number of partitions of data implied by the first tree but not the second tree and B is the number of partitions of data implied by the second tree but not the first tree (although some ...
The near field is remarkable for reproducing classical electromagnetic induction and electric charge effects on the EM field, which effects "die-out" with increasing distance from the antenna: The magnetic field component that’s in phase quadrature to electric fields is proportional to the inverse-cube of the distance (/) and electric field ...
The comoving distance from an observer to a distant object (e.g. galaxy) can be computed by the following formula (derived using the Friedmann–Lemaître–Robertson–Walker metric): = ′ (′) where a(t′) is the scale factor, t e is the time of emission of the photons detected by the observer, t is the present time, and c is the speed of ...
where n is the local refractive index as a function of distance along the path C. An electromagnetic wave propagating along a path C has the phase shift over C as if it was propagating a path in a vacuum , length of which, is equal to the optical path length of C .
The distance (or perpendicular distance) from a point to a line is the shortest distance from a fixed point to any point on a fixed infinite line in Euclidean geometry. It is the length of the line segment which joins the point to the line and is perpendicular to the line. The formula for calculating it can be derived and expressed in several ways.
In its simplest form, the path loss can be calculated using the formula L = 10 n log 10 ( d ) + C {\displaystyle L=10n\log _{10}(d)+C} where L {\displaystyle L} is the path loss in decibels, n {\displaystyle n} is the path loss exponent, d {\displaystyle d} is the distance between the transmitter and the receiver, usually measured in meters ...