near-field approximation

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• Near and far field — This article is about the electromagnetic concept. For the mathematical, see Near field (mathematics). Antenna field regions for antennas that are shorter than the wavelength of the radiation they emit, such as the whip antenna of a citizen s… …   Wikipedia

• Field emission — (FE) is the emission of electrons from the surface of a condensed phase into another phase due to the presence of high electric fields. In this phenomenon, electrons with energies below the Fermi level tunnel through the potential barrier at the… …   Wikipedia

• Field of view — The field of view (also field of vision) is the angular extent of the observable world that is seen at any given moment.Different animals have different fields of view, depending on the placement of the eyes. Humans have an almost 180 degree… …   Wikipedia

• Polymer field theory — A polymer field theory within the framework of statistical mechanics is a statistical field theory, describing the statistical behavior of a neutral or charged polymer system within the field theoretic approach.It can be derived by transforming… …   Wikipedia

• Depth of field — The area within the depth of field appears sharp, while the areas in front of and beyond the depth of field appear blurry …   Wikipedia

• Magnetic field — This article is about a scientific description of the magnetic influence of an electric current or magnetic material. For the physics of magnetic materials, see magnetism. For information about objects that create magnetic fields, see magnet. For …   Wikipedia

• Rotating wave approximation — The rotating wave approximation is an approximation used in atom optics and magnetic resonance. In this approximation, terms in a Hamiltonian which oscillate rapidly are neglected. This is a valid approximation when the applied electromagnetic… …   Wikipedia

• Earth's magnetic field — Computer simulation of the Earth s field in a normal period between reversals.[1] The tubes represent magnetic field lines, blue when the field points towards the center and yellow when away. The rotation axis of the Earth is centered and… …   Wikipedia

• geomagnetic field — Magnetic field associated with the Earth. It is essentially dipolar (i.e., it has two poles, the northern and southern magnetic poles) on the Earth s surface. Away from the surface, the field becomes distorted. Most geomagnetists explain the… …   Universalium

• Oseen's Approximation — In 1910 Carl Wilhelm Oseen proposed Oseen s Approximation to treat problems in which a flow field consists of small disturbance of a constant mean flow. His work was based on the experiments of Navier Stokes. Stokes studied a sphere of radius “a” …   Wikipedia

• Fresnel diffraction — In optics, the Fresnel diffraction equation for near field diffraction, is an approximation of Kirchhoff Fresnel diffraction that can be applied to the propagation of waves in the near field.[1] The near field can be specified by the Fresnel… …   Wikipedia