Fr.: adhérer, être cohérent
1) To stick together; be united; hold fast, as parts of the same mass.
From L. cohaerere "to cleave together," from → com- "together," + haerere "to stick."
The property of two or more electromagnetic waves when they are in fixed phase relationship over time. If the crests and troughs of the waves meet at the same time and place they are said to be in phase.
Fr.: zone de cohérence
Of an electromagnetic wave, the area of a surface perpendicular to the direction of propagation, over which the electromagnetic wave maintains a specified degree of coherence.
Fr.: longueur de cohérence
The distance over which an electromagnetic wave train maintains a specified degree of coherence.
Fr.: temps de cohérence
The time over which a propagating electromagnetic wave may be considered coherent. The coherence time of an interferometer is the interval during which the fringe phase remains stable.
Two or more wave sources are said to be coherent sources if the phase difference between a pair of points, one in each source, remains constant.
Coherent, adj., → coherence.
nur-e hamdus (#)
Fr.: lumière cohérente
Light waves that have the same wavelength and possess a fixed phase relationship, as in a laser.
Fr.: optique cohérente
A branch of optics that uses coherent radiation to produce holographic three-dimensional images of objects.
Fr.: diffusion cohérente
A scattering process in which the scattered radiation bears the same frequency and phase as the incident radiation.
Fr.: source cohérente
One of two light beams derived from the same source in → interference experiments. It is impossible to obtain interference from two separate sources because their → wavefronts do not have a constant → phase difference. In → Young's experiment, → Fresnel's biprism, → Fresnel's mirrors, and → Lloyd's mirror the two sources always have a point-to-point correspondence of phase, since they are both derived from the same source.
mowjhâ-ye nâhamdus (#)
Fr.: ondes incohérentes
The lack of a fixed phase relationship between two or more waves. → coherent.
tâbeš-e nâhamdus (#)
Fr.: rayonnement incohrént
Radiation having waves that are out of phase in space and/or time; radiation which is not → coherent.
Fr.: diffusion incohérente
The absorption of a photon and its re-emission at a different frequency (in the observer's frame of reference) by scattering atoms.
Fr.: cohérence spatiale
In a wave train, a correlation between the phases of waves at points separated in space at a given time.