Preferred Label : irradiance (at a point of a surface);
Detailed label : irradiance (at a point of a surface), E;
IUPAC definition : radiant power, P, 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 W m-2.;
Scope note : e ¿ ¿ e¿ where e¿is the spectral irradiance at wavelength¿.; 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 (eo) is an equivalent term.; alternative definition: integral, taken over the hemisphere visible from the given
point, of the expression l ¿ ¿ ,where l is the radiance at the given
point in the various directions of the incident elementary beams of solid angle¿ and¿
is the angle between any of the beams and the normal to the surface at the given point.
e 2p ¿ l ¿; mathematical definition: e s p .if the radiant power
is constant over the surface area considered, e p s
.;
Origin ID : I03254;
See also
radiant power, P, 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 W m-2.
