— disturbances (changes of the environment or field) propagating through space with finite speed. Depending on the shape of the wave surface distinguish plane waves and spherical waves. Distribution W. described the wave equation and perturbation dependence on the coordinates and time — W. equation.

— waves that describe the state of microparticles (electrons, atoms, molecules, etc.). reflecting the quantum nature of microparticles wave-particle duality of their properties. Each pulse of microparticles with a momentum $\vec{p}$ and energy $E$ corresponds De B.w. of frequency $\nu=\dfrac{E}{h}$ and the wavelength $\lambda=\dfrac{h}{p}$, where $h$ — Planck constant.Development of concepts of De B.w.

— channel for wave propagation. There are acoustic H. as pipes, rods and fibers radio waves in a dielectric channels of different shapes and others.

— a natural system of units, which are the basic units of charge and rest mass of the electron, the radius of the first Bohr orbit of the hydrogen atom $a_{0}=(0.52917706 \pm 0.00000044) \cdot 10^{10} \mathrm{m}$ and Planck constant. The proposed Eng. scientist D. Hartree (1897-1958). Is used in nuclear physics.

1. The old Russian unit of length that applied before the introduction of the metric system of weights. $1 \mathrm{F}=12 \mathrm{inches}=0.3 \mathrm{m}$.
2. British unit of length. $1 \mathrm{F}=12 \mathrm{inches}=\dfrac{1}{3} \mathrm{Yard}=304.8 \mathrm{mm}$.

1. The old Russian unit of mass and weight, which was used before the introduction of the metric system of weights. $1\mathrm{LB}=\dfrac{1 }{ 40}\ \mathrm{pud}=409.512 \mathrm{g}$.
2. British unit of weight equal to $0.453592$kg (commercial LB).

— correspondence between the sets of the independent variable (argument) $x$ and the dependent variable (function) $y$, in which each element of the set $x$ corresponds to one and only one element of the set $y$. Such a correspondence between $x$ and $y$ is denoted $$y=f(x)$$ F. can be set analytically (formulas) graphically (chart) or tabular. F. expressing many quantitative laws of physics.

— a system of basic ideas, principles and guidelines, allowing on the basis of a small number of fundamental physical laws (starts) explain and provide an unlimited number of certain physical phenomena and solve many prykladnh tasks. By F. ph. th. include classical mechanics,electrodynamics, relativity theory, quantum mechanics, statistical physics and thermodynamics.

— hypothetical microcosm constant, which determines the size of the area in which there are laws that do not fit into the framework of modern quantum theory. According to research estimates F. d. About less than $10^{-22}$ m.

— the same as eddy currents. Named after the French. physics JB Foucault (1819-1868).