IUPAC Gold Book - irradiance (at a point of a surface), E

irradiance (at a point of a surface), $Math - title$

Radiant power, $Math - ei$ , of all wavelengths incident from all upward directions on a small element of surface containing the point under consideration divided by the area of the element. SI unit is $Math - ei$ .

Notes:

Mathematical definition: $Math - ei$ . If the radiant power is constant over the surface area considered, $Math - ei$ .
Alternative definition: Integral, taken over the hemisphere visible from the given point, of the expression $Math - ei$ , where $Math - ei$ is the radiance at the given point in the various directions of the incident elementary beams of solid angle $Math - ei$ and $Math - ei$ is the angle between any of the beams and the normal to the surface at the given point.
$Math - e$
This term refers to a beam not scattered or reflected by the target or its surroundings. For a beam incident from all directions, fluence rate ( $Math - ei$ ) is an equivalent term.
$Math - ei$ where $Math - ei$ is the spectral irradiance at wavelength $Math - ei$ .

Source:

PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 357

Related index:

IUPAC > Gold Book > math/physics > quantities

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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.

Last update: 2008-10-07; version: 2.0.2.

DOI of this term: doi:10.1351/goldbook.I03254.

Original PDF version (may be out of date): http://www.iupac.org/goldbook/I03254.pdf.

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