An Etymological Dictionary of Astronomy and Astrophysics
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The wavelength in a given diffraction order for which the efficiency curve reaches its maximum.

→ blaze; → wavelength.

Mowjtul→ wavelength; beliz→ blaze.

Center of a filter passband measured at 50% of peak transmittance.

→ center; → wavelength.

1) In an interference filter, the wavelength of peak transmission.
2) In a spectrograph, the wavelength corresponding to the middle of the range covered by the grating or grism.

Central, adj. from → center; → wavelength.

The quantum wavelength of a particle with a highly relativistic velocity. The Compton wavelength is given by h/mc, where h is Planck's constant, m is the mass of the particle, and c the light speed. For an electron, the Compton wavelength is about 2.4 × 10^-10 cm, intermediate between the size of an atomic nucleus and an atom.

→ Compton; → wavelength.

Wavelength at which the transmittance of a filter, or the detectivity of a detector, has fallen to one-half its peak value.

→ cutoff; → wavelength.

The wavelength of the wave associated with a → particle as given by the → de Broglie equation.

→ de Broglie equation; → wavelength.

Deriving the → wavelength of an undulatory phenomenon from its → frequency, and vice versa.
1) For → electromagnetic waves: λ = c / f, where λ is the wavelength, c is the → speed of light in → meters per second and f the frequency in → hertz. It can be written as: λ (m) = 2.998 × 10⁸ / f (Hz).
2) For → sound waves: λ = C / f, where C is the → sound speed. For air at temperature 0°C, λ (m) = 332 / f (Hz).

→ frequency; → wavelength; → conversion.

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

→ peak; → wavelength.

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

→ radio; → wavelength.

The distance between two successive points in the wave that are characterized by the same phase of oscillation; e.g. → de Broglie wavelength; → Compton wavelength; → blaze wavelength; → peak wavelength; → center wavelength; → central wavelength; → cutoff wavelength.

→ wave; → length.

A small wave; ripple.

→ wave + -let a diminutive suffix.

A refinement of → Fourier analysis which enables to simplify the description of a complicated function in terms of a small number of coefficients. The formal history of wavelet theory began in the early 1980s when Jean Morlet, a French geophysicist, introduced the concept of wavelet and studied wavelet transform as a new tool for scientific signal analysis. In 1984, his collaboration with Alex Grossmann yielded a detailed mathematical study of the continuous wavelet transforms and their various applications. Although similar results had already been obtained 20-50 years earlier by several other researchers, the rediscovery of the old concepts provided a new method for decomposing functions.

→ wavelet; → theory.