- See also list of optical topics.
Optics (appearance or look in ancient Greek) is a branch of physics that describes the behavior and properties of light and the interaction of light with matter. Optics explains and is illuminated by optical phenomena.
The field of optics usually describes the behavior of visible, infrared and ultraviolet light; however since light is an electromagnetic wave, analogous phenomena occur in X-rays, microwaves, radio waves, and other forms of electromagnetic radiation. Optics can thus be regarded as a sub-field of electromagnetism. Some optical phenomena depend on the quantum nature of light and as such some areas of optics are also related to quantum mechanics.
Optics, however, as a field is often considered largely separate from the physics community. It has its own identity, societies, and conferences. The pure science aspects of the field are often called Optical Science or Optical Physics. Applied optical sciences are often called optical engineering. Applications of optical enginering related specifically to illumination systems is called illumination engineering. Each of these disciplines tends to be quite different in its applications, technical skills, focus, and professional affiliations.
Because of the wide application of the science of "light" to real-world applications, the area of optical science, and optical engineering tends to be very cross-disiplinary. You will find optical science a part of many related disciplines including electrical engineering, physics, psychology, medicine, and others.
Classical or geometric optics, sometimes called ray optics is the branch of optics that describes light propagation in terms of rays.
Rays are bent at the interface between two dissimilar media, and may be curved in a medium in which the refractive index is a function of position.
The ray in geometric optics is perpendicular to the wavefront in physical optics .
Modern Optics is a term used to describe areas of optical science and engineering that became popular in the 20th century. These areas of optical science typically relate to the electromagnetic or quantum properties of light but do include other topics.
Other optical fields
Optics is part of everyday life. Rainbows and appearances of fata Morgana or the green ray are examples of optical phenomena.