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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 .
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 ...
In his 1911 paper , Rutherford assumed that the central charge of the atom was positive, but a negative charge would have fitted his scattering model just as well. [34] In a 1913 paper, [ 35 ] Rutherford declared that the "nucleus" (as he now called it) was indeed positively charged, based on the result of experiments exploring the scattering ...
Moseley's law. 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 ...
In elementary algebra, the binomial theorem (or binomial expansion) describes the algebraic expansion of powers of a binomial.According to the theorem, it is possible to expand the polynomial (x + y) n into a sum involving terms of the form ax b y c, where the exponents b and c are nonnegative integers with b + c = n, and the coefficient a of each term is a specific positive integer depending ...
The mass-to-charge ratio ( m / Q) is a physical quantity relating the mass (quantity of matter) and the electric charge of a given particle, expressed in units of kilograms per coulomb (kg/C). It is most widely used in the electrodynamics of charged particles, e.g. in electron optics and ion optics .
Canonical commutation relation. In quantum mechanics, the canonical commutation relation is the fundamental relation between canonical conjugate quantities (quantities which are related by definition such that one is the Fourier transform of another). For example,
All that is left is the constant term −1/12, and the negative sign of this result reflects the fact that the Casimir force is attractive. [ 20 ] A similar calculation is involved in three dimensions, using the Epstein zeta-function in place of the Riemann zeta function.