optics

Optics is the branch of physics which deals with the nature and propagation of light, including refraction, dispersion and wave property of light such as interference, diffraction, and polarization. Light is a form of energy. It can be divided into two categories: visible and invisible light. The visible light on entering our eyes produces the sensation of sight. But light in the invisible region doesn’t produce sensation of sight. Any object that emits light is called source of light. There are two sources of light :(a) self-luminous: an object which possesses light of its own is called self-luminous. E.g.: sun, stars, candle, glowing electric bulbs etc. (b) non-luminous: It is the source of light which doesn’t possesses light of its own but it receives light from other sources and then reflects or scatters to the surroundings. E.g.: moon, planets, book, papers etc.
Any substances through which light passes (or propagate) is called medium.eg: water, glass, plastic, etc. the along which light travels is called a ray. The combination of number of rays is called beam. If a light ray is reversed, it always travels along its original path. Thus optics is branch of science which is very useful in our daily life.