Optics is a branch of physics that studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light, but other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties. There are two major branches of optics: physical and geometrical.

• Physical Optics: This branch of optics deals primarily with the nature and properties of light itself. It is a more comprehensive model of light, which includes wave effects such as diffraction and interference that cannot be accounted for in geometrical optics.

• Geometrical Optics: This branch of optics has to do with the principles that govern the image-forming properties of lenses, mirrors, and other devices that make use of light. In geometrical optics, light is considered to travel in straight lines, while in physical optics, light is considered as an electromagnetic wave. Geometrical optics can be viewed as an approximation of physical optics that applies when the wavelength of the light used is much smaller than the size of the optical elements in the system being modeled.

Optics has many applications in various fields, including medicine, telecommunications, and astronomy.