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Bessel's correction. In statistics, Bessel's correction is the use of n − 1 instead of n in the formula for the sample variance and sample standard deviation, [1] where n is the number of observations in a sample. This method corrects the bias in the estimation of the population variance. It also partially corrects the bias in the estimation ...
The electric charge Q, third component of weak isospin T 3 (also called T z, I 3 or I z) and weak hypercharge Y W are related by = +, (or by the alternative convention Q = T 3 + Y W). The first convention, used in this article, is equivalent to the earlier Gell-Mann–Nishijima formula .
In condensed matter physics and crystallography, the static structure factor (or structure factor for short) is a mathematical description of how a material scatters incident radiation. The structure factor is a critical tool in the interpretation of scattering patterns ( interference patterns) obtained in X-ray, electron and neutron ...
Negative refraction. Negative refraction is the electromagnetic phenomenon where light rays become refracted at an interface that is opposite to their more commonly observed positive refractive properties. Negative refraction can be obtained by using a metamaterial which has been designed to achieve a negative value for (electric) permittivity ...
The fine-structure constant, α, has several physical interpretations. α is: The ratio of two energies: the energy needed to overcome the electrostatic repulsion between two electrons a distance of d apart, and. the energy of a single photon of wavelength λ = 2πd (or of angular wavelength d; see Planck relation ): α = ( e 2 4 π ε 0 d ...
The rms charge radius is a measure of the size of an atomic nucleus, particularly the proton distribution. The proton radius is about one femtometre = 10−15 metre. It can be measured by the scattering of electrons by the nucleus. Relative changes in the mean squared nuclear charge distribution can be precisely measured with atomic spectroscopy .
Moseley's law is an empirical law concerning the characteristic X-rays emitted by atoms. The law had been discovered and published by the English physicist Henry Moseley in 1913–1914. [1] [2] Until Moseley's work, "atomic number" was merely an element's place in the periodic table and was not known to be associated with any measurable ...
Analytic continuation around the pole at s = 1 leads to a region of negative values, including ζ(−1) = − + 1 / 12 . In zeta function regularization , the series ∑ n = 1 ∞ n {\textstyle \sum _{n=1}^{\infty }n} is replaced by the series ∑ n = 1 ∞ n − s . {\textstyle \sum _{n=1}^{\infty }n^{-s}.}