An Etymological Dictionary of Astronomy and Astrophysics
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A type of electrically operated oven that cooks food very quickly using microwaves instead of heat.

→ microwave; → oven.

Electromagnetic radiation carried by → microwaves.

→ microwave; → radiation.

Microwaves with wavelengths between 1 and 10 millimeter, corresponding to frequencies between 300 GHz to 30 GHz. → millimeter-wave astronomy.

→ milli-; → meter; → wave.

That part of radio astronomy which uses electromagnetic waves in the range 1-10 millimeter to study various components of the Universe, in particular the chemistry of interstellar matter.

→ millimeter wave; → astronomy.

A combination of two or more waves resulting in the production of frequencies not present in the original waves, the new frequencies being usually the sums and differences of integral multiples of the frequencies in the original waves.
A wave which varies in some characteristic in accordance with the variations of a modulating signal. Compare continuous wave. See modulation

Modulated, p.p. of → modulate; → wave.

A large-scale → shock wave observed in Hα on the Sun's → chromosphere that is generated by the impact of a → solar flare. Moreton waves expand outward at about 1,000 km/s, and may travel for several hundred thousand kilometers. They are accompanied by meter-wave radio bursts.

Named after the American astronomer Gail E. Moreton (1960, A.J. 65, 494); → wave.

Same as → neutral mode.

→ neutral; → wave.

→ compressional wave.

P, referring to → pressure; → wave.

The wavelength at which the radiant intensity of a source is maximum.

→ peak; → wavelength.

An oscillatory motion in which each point is repeatedly displaced at equal time intervals.

→ periodic + → wave.

A wave whose wavefronts of constant phase are infinite parallel planes normal to the direction of propagation.

→ plane; → wave.

A plate of doubly refracting material cut parallel to the optic axis of the crystal and of such a thickness that a phase difference of 90° is introduced between the ordinary and extraordinary rays for light of a particular wavelength. → half-wave plate.

→ quarter; → wave; → plate.

The → electromagnetic radiation with the longest → wavelengths (and lowest energies), ranging from 0.3 mm to several km. Radio waves form a very broad category, which includes the → submillimeter waves (with a wavelength of 0.3-1 mm) and → microwave regions (1 mm to several cm).

→ radio; → wave.

The → electromagnetic radiation with a wavelength ranging from 1 mm to several 100 km. See so → radio wave.

→ radio; → wavelength.

A pressure wave in a fluid generated by rarefaction. It travels in the opposite direction to that of a shock wave in the medium.

→ rarefaction; → wave.

An ordinary electromagnetic wave that goes forward with time. → Maxwell's equations are indifferent to the distinction between past and future. It is therefore permissible for the electromagnetic waves to go backward in time. Forward-in-time waves are called retarded, as they arrive after they are sent by the transmitter. Backward-in-time waves are called → advanced wave.

Retarded, adj. of → retard; → wavel.

A wave on a uniform current in a two-dimensional non-divergent fluid system, rotating with varying angular speed about the local vertical.

→ Rossby number; → wave.

→ shear wave.

S, referring to → shear; → wave.

In theories of gravitation, a kind of → gravitational wave, transversal and/or longitudinal, characterized by → spin zero.

→ scalar; → wave.

An → elastic wave generated in the → Earth by an → impulse such as an → earthquake or an → explosion. Seismic waves may travel either along or near the Earth's surface or through the Earth's interior.

→ seismic; → wave.