At a point on a surface and in a given direction, the
radiant intensity of an element of the surface, divided by the area of the orthogonal projection this element on a plane perpendicular to the given direction.
Source:
ISO 31-5: 1992
(Quantities and Units - Part 5: Electricity and Magnetism.)
See also:
PAC, 1996, 68, 2223
(Glossary of terms used in photochemistry (IUPAC Recommendations 1996))
on page 2268
Orange Book, p. 120
PAC, 1990, 62, 2167
(Glossary of atmospheric chemistry terms (Recommendations 1990))
on page 2208
Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A.Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8.
doi:10.1351/goldbook.
