17-24-008

directional emissivity

ε; ε(θ, φ)

quotient of the radiance of a thermal radiator in a given direction and the radiance of a Planckian radiator at the same temperature

Note 1 to entry: The symbols θ, φ are chosen here as an example of the angular coordinates defining the given direction.

Note 2 to entry: The directional emissivity has unit one.

Note 3 to entry: This entry was numbered 845-04-08 in IEC 60050-845:1987.

Note 4 to entry: This entry was numbered 17-328 in CIE S 017:2011.

Publication date: 2020-12