Ray optics(geometrical optics) concerns itself with particle nature of light and is based on
- rectilinear propagation of light and
- the laws of reflection and refraction of light.
It explains the formation of images in mirrors and lenses, the aberrations of optical images and the working and designing of optical instruments.
Behaviour of light at interface of two media
When light travelling in one medium falls on the surface of second medium, the following three effects may occur:
- A part of incident light is turned back into the first medium. This is called reflection of light.
- A part of incident light is transmitted into the second medium along a changed direction. This is called refraction of light.
- The remaining third part of light energy is absorbed by the second medium. This is called absorption of light.
Laws of reflection of light
Reflection of light takes place according to the following two laws:
- The angle of incidence is equal to the angle of reflection, i.e., ∠i = ∠r.
- The incident ray, the reflected ray and the normal at the point of incidence all lie in the same plane.
The above laws of reflection are valid for both plane and curved reflecting surfaces.