An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The partial differential equation ∂²U / ∂²x + ∂²U / ∂²y + ∂²U / ∂²z = (1/c²) ∂²U / ∂²t or its counterparts in one or two dimensions or in other coordinates, the solution of which represents the propagation of displacementU as waves with velocity c.

→ wave; → equation.

In → quantum mechanics, the function of space and time that satisfies → Schrodinger equation. The square of the modulus of its amplitude at any point represents the probability of finding a particle there.

→ wave; → function.

One of the forms of quantum mechanics, due to Louis de Broglie and extended by E. Schrödinger. It originated in the suggestion that light consists of corpuscles as well as of waves and the consequent suggestion that all elementary particles are associated with waves.

→ wave; → mechanics

A general term to describe → light involving the following phenomena: → reflection, → refraction, → interference, → diffraction, and → polarization. Compare → particle nature.

→ wave; → nature.

The reciprocal of → wavelength, which represents the number of waves per unit length. Wave number is often defined as k = 2π/λ. Same as → propagation number.

→ wave; → number

The branch of optics that analyzes the electromagnetic radiation in terms of its wave characteristics. Also called → physical optics.

→ wave; → optics.

A traveling → waveform consisting of the → superposition of several → waves of different → wavelengths and → phases.

→ wave; packet from M.E. pak "bundle" + diminutive suffix -et; maybe from M.Fr. pacquet.

Basté "packet," literally "bound, tied; set," p.p. of bastan "to form, bind, tie" (Mid.Pers. bastan/vastan "to bind, shut;" Av./O.Pers. band- "to bind, fetter," banda- "band, tie;" cf. Skt. bandh- "to bind, tie, fasten;" Ger. binden; E. bind; PIE base *bhendh- "to bind").

An optical element that retards the phase of one plane of vibration of light relative to the plane at right angles. The two beams then recombine to form a single beam with new polarization characteristics. A typical wave plate is a birefringent crystal with a carefully chosen orientation and thickness. Also known as → retardation plate. A → half-wave plate creates a half-wave retardation. See also → quarter-wave plate.

→ wave; → plate.

The theory that describes light as waves that spread out from the source that generates the light. It contradicts the → corpuscular theory of light proposed by Newton (1704). The idea of the wave nature of light was first put forward by Robert Hooke (1660). The wave theory was originally stated by Huygens (1690), who showed reflection and refraction could be explained by this theory. It was supported by → Young's experiment (1802) and established by the work of Fresnel (1814-1815). The wave theory received its most important support from Maxwell's → electromagnetic theory. See also → Huygens-Fresnel principle.

→ wave; → theory; → light.

A series of successive waves spaced at regular intervals.

→ wave; → train.

A vector whose direction is that of propagation of a wave and whose magnitude is given by the → wave number, 2π/λ, where λ is the → wavelength, or ω/c, where ω is the → angular frequency and c is the speed of propagation.

→ wave; → number.

The principle admitted in → quantum mechanics that all particles have a wave-like nature and that waves have a particle aspect. The wave-particle duality is of fundamental importance in obtaining a realistic picture of the → elementary particles.
See also: → particle nature, → wave nature, → de Broglie hypothesis, → Davisson-Germer experiment.

→ wave; → particle; → duality.

A portion of the electromagnetic spectrum which is defined because of its characteristics or for its use.

→ wave; → band.

A graphical representation of the shape of a wave for a given instant in time.

→ wave; → form.

The resolution of a complex waveform into a sum of simple periodic waves, usually by computer means.

→ waveform; → analysis.

The locus of adjacent points possessing the same phase in the path of a wave motion. Its surface is uniform (spherical or plane) and normal to propagation direction in an isotropic medium. → wavefront distortion.

→ wave; → front.

In → adaptive optics, eliminating the effects of atmospheric turbulence on the wavefront of the object being observed. → wavefront distortion.

→ wavefront; → correction.

The disruption of the spherical shape of a wavefront due to atmospheric turbulence which makes the adjacent points in the wavefront out of phase.

→ wavefront; → distortion.

In adaptive optics, a device that analyzes the light sample coming from the wavefront and determines the error in each part of the beam. The wavefront sensor used in adaptive optics is a → Shack-Hartmann type, which works in conjunction with a deformable mirror.

→ wavefront; → sensor.

The average slope in both the X and Y directions of a → wavefront or phase profile across the pupil of an optical system.

→ wavefront; → tilt.