RADIANCE
Definition
A <RADIANCE> is a <RADIANT FLUX> that is emitted, reflected, transmitted or received by a given surface, per unit solid angle per unit projected area. It is calculated as L = (dI/dA) .(1/cos(alpha)) where dI is the radiant intensity emitted from an element of a <SURFACE> with <AREA> dA and <ANGLE> alpha is an <ANGLE> between the normal to a <SURFACE> and the given direction