Radiosity is an old term for radiant exitance.
Radiant emittance is an old term for radiant exitance.
(Terms of radiometry)
The radiant flux per unit area at a point on a surface, where the surface can be real or imaginary (a mathematical plane). An imaginary surface can for example be used to calculate or measure radiant flux density anywhere in space.
There are two cases:
Irradiance (usually Ei in formulas) is the total amount of radiative flux incident upon a point on a surface from all directions above the surface.
Irradiance weighted with the response curve of the human eye gives Illuminance.
Radiant exitance is the total amount of radiative flux leaving a point on a surface into all directions above the surface.
Radiant exitance weighted with the response curve of the human eye gives Luminous Exitance.
Standard unit of all forms of radiant flux density is watts per square meter (W/m2).
luminous flux density
|radiant flux density||Die Strahlungsflussdichte|
|radiant exitance||Die spezifische Ausstrahlung|