degree of coherence — An Etymological Dictionary of Astronomy and Astrophysics

degree of coherence

درجه‌ی ِ همدوسی

dareje-ye hamdusi

Fr.: degré de cohérence

The extent of → coherence of an → electromagnetic wave, as indicated by a → dimensionless number.

Since interference takes place when waves are → coherent, using a → Young’s experiment, the degree of coherence
is measured from the → fringe → visibility, V. It is defined as the ratio V = (I_max - I_min) / (I_max + I_min), where I_max is the intensity at a maximum of the → interference pattern, and I_min is the intensity at a minimum of the interference pattern.

The electromagnetic wave is considered to be highly coherent when the degree of coherence is about 1, incoherent for nearly zero values, and partially coherent for values between 0 and 1.

See also: → degree; → coherence.

An Etymological Dictionary of Astronomy and Astrophysics

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