Illumination

The illumination of a plane at a given point is the incident flux per unit surface in this plane, at the point considered. We therefore have

E = Φ A R size 12{E= { {Φ} over {A rSub { size 8{R} } } } } {}

where \(A_{R}\) is the illuminated surface. Illuminance is expressed in \(\text{Wm}^{-2}\).