# Irradiance

**1-1-140**

Irradiance (at a point of a surface)

The quotient of the radiant flux (dOe) incident on an element of the surface containing the point, by the area (dA) of that element.

Symbol Ee

Unit watt per square metre (W/m2)

Reference: C.I.E. (modified)

Note: If the radiant flux Fe may be considered uniformly distributed over a finite plane surface of area A, the irradiance on this surface is given by ?? where Fe is the total radiant flux incident on the surface.

*Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)*

square metre

Contrast

Celsius (previously Centigrade)

Capacitance

charge current

Intensity

Illuminance

Energy

nertia of the water plane

ampere

International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM