| 释义 |
optical depth
optical depth Symbol: τ. A measure of the absorption of radiation of a particular wavelength as it passes through a gaseous medium. If the initial radiation flux Φ0 is reduced to Φx after a distance x through the medium then Φx /Φ0 = exp(–τ) where τ is the optical depth for the radiation wavelength. If τ equals zero the medium is transparent; if τ is much greater or much less than one the medium is optically thick or optically thin respectively. See also opacity.optical depth[′äp·tə·kəl ′depth] (meteorology) optical thickness |