An Etymological Dictionary of Astronomy and Astrophysics
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The angle between the → incident ray of light entering an → optical system (such as a prism) and the → refracted ray that emerges from the system. Because of the different indices of refraction for the different wavelengths of visible light, the angle of deviation varies with wavelength.

→ angle; → deviation.

The angle between the light entering and exiting the prism when the light passing through the prism is parallel to the prism's base. Angle of minimum deviation (D) is used to measure the → index of refraction (n) of the prism glass, because: n = sin [(A + D)/2]/sin (A/2), where A is the → prism angle.

→ angle; → minimum; → deviation.

The act of deviating; departure from a standard or norm.
Statistics: The difference between a datum and some reference value, typically the mean of the data. → standard deviation.

Verbal noun form of → deviate.

Same as → angle of minimum deviation.

→ minimum; → deviation.

The most widely used measure of dispersion of a frequency distribution. It is equal to the positive square root of the → variance. Same as → standard error. Not to be confused with the → root mean square error.

→ standard; → deviation.