 The CGS unit erg per square centimeter per second () is often used in astronomy.Radiosity is often called  in branches of physics other than radiometry, but in radiometry this usage leads to confusion with radiant intensity.Radiosity of a "surface", denoted "J"e ("e" for "energetic", to avoid confusion with photometric quantities), is defined as
where

For an "opaque" surface, the "transmitted" component of radiosity "J"e,tr vanishes and only two components remain