Optics

Optics is the study of the behavior and properties of light including its interactions with matter and its detection by instruments. The word optics comes from ὀπτική, meaning appearance or look in ancient Greek.
Even when still completely classical, complete electromagnetic descriptions of optical behavior are often difficult to apply to practical problems. This is why particular simplified models are used instead, notably those of geometrica optics and physical optics. These limited models adequately describe large subsets of optical phenomena while ignoring behavior that is insignificant for the system of interest.
The pure science of optics is called optical science or optical physics to distinguish it from applied optical sciences, which are referred to as optical engineering. Prominent subfields of optical engineering include illumination engineering, photonics, and optoelectronics.
Some of these fields overlap, with nebulous boundaries between the subjects terms that mean slightly different things in different parts of the world and in different areas of industry. A professional community of researchers in nonlinear optics has developed in the last several decades due to advances in laser technology.Optical science is relevant to and studied in many related disciplines including electrical engineering, psychology, and medicine (particularly ophthalmology and optometry).