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

A radio emission with a negative → spectral index. In this type of emission the intensity of the emitted radiation increases with wavelength.

→ non-thermal; → spectrum.

Same as → blackbody spectrum.

→ Planck; → spectrum.

The plot that gives the portion of a signal's power falling within given frequency bins. The most common way of generating a power spectrum is by using a discrete Fourier transform.

→ power; → spectrum.

The spectrum formed by a dispersing prism or a dispersing prism system.

Adj. of → prism + → spectrum.

The components of radiation arranged in order of their wavelengths, frequencies, or quantum energies. For particle radiation they are arranged in order of their kinetic energies.

→ radiation; → spectrum.

That part of the → electromagnetic spectrum that includes → radio waves.

→ radio; → spectrum.

The part of → electromagnetic spectrum approximated by the → Rayleigh-Jeans law.

→ Rayleigh; → Jeans; → spectrum.

A spectrum after correction for detector's → baseline.

Rectified p.p. of → rectify; → spectrum.

The spectrum of a molecule resulting from the simultaneous rotation and vibration of its constituent atoms.

→ rotation; → vibration; → spectrum.

The spectrum of the Sun's electromagnetic radiation, consisting of a continuum spectrum marked with dark absorption lines.

→ solar; → spectrum.

The emission spectrum produced through a gas or vapor as a result of a high-voltage discharge between metallic electrodes.

→ spark; → spectrum.

The → electromagnetic radiation divided into its constituting wavelengths or frequencies.

From L. spectrum "appearance, image, apparition," from specere "to look at, view;" Gk. skopein "to behold, look, consider," skeptesthai "to look at;" PIE base *spek- "to see;" cf. Av. spas-, spaš- "to attend to; to serve; spy," spasiieiti "looks at, perceives" (Mod.Pers. sepâs "kindness, favor, thanksgiving," sepâsidan "to praise for benefits received);" Skt. paś- "to see, watch," spasati "sees;" L. specere "to look at;" O.H.G. spehônn "to spy," Ger. spähen "to spy."

Binâb "a vision;" Mid.Pers. wênâb "vision," from wên-, present stem of didan "to see;" O.Pers. vain- "to see;" Av. vaēn- "to see;" cf. Skt. veda "I know;" Gk. oida "I know," idein "to see;" L. videre "to see;" PIE base *weid- "to know, to see."

The portion of → electromagnetic spectrum corresponding to → visible light.

→ visible; → spectrum.