From M.E. depthe, from O.E. deop "deep," → deep + -the "-th."
Žarfâ, noun of žarf "deep," → deep + -â.
Fr.: profondeur équivalente
A measure of the number of particles passing a given point in a → planetary ring per unit time. It is obtained by multiplying the physical width of the ring by its average → optical depth. For the variable-width eccentric rings of → Uranus, equivalent depth remains almost constant around a given ring (Ellis et al., 2007, Planetary Ring Systems, Springer).
Fr.: profondeur optique
1) A measure of how much radiation is absorbed when traveling through a medium
(such as the atmosphere of a star or the interstellar medium) from the source to a
given point. It depends on the type of medium and the frequency of radiation.
It is defined as a dimensionless quantity
dτλ = κλ ρ dx,
where κλ is the
extinction coefficient, ρ the density, and dx the path length.