This usage tends not to include effects such as quantum noise in optical communication, which is studied in the sub-branch of coherence theory.
This is useful for bodies with large smooth convex shapes and for lossy (low-reflection) surfaces.
The ray-optics field or current is generally not accurate near edges or shadow boundaries, unless supplemented by diffraction and creeping wave calculations.
The standard theory of physical optics has some defects in the evaluation of scattered fields, leading to decreased accuracy away from the specular direction.
[2][3] An improved theory introduced in 2004 gives exact solutions to problems involving wave diffraction by conducting scatterers.