In optics the noise-equivalent flux density (NEFD) or noise-equivalent irradiance (NEI) of a system is the level of flux density required to be equivalent to the noise present in the system. It is a measure used by astronomers in determining the accuracy of observations.
Famous quotes containing the word flux:
“Existence is no more than the precarious attainment of relevance in an intensely mobile flux of past, present, and future.”
—Susan Sontag (b. 1933)