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GEOMETRICAL OPTICS

The branch of optics dealing with such optical phe­nomena as reflection and refraction is called geometrical optics, because it compares light "rays" with the directed straight lines called rays in geometry. The basic principles and equations of reflection and refraction are derived from the assumption of simple geometric and trigonomet­ric relations between incident and reflected and incident and refracted light rays.

Light leaves a source as an indefinite number of par­ticles travelling in straight lines. We call the path fol­lowed by any one of these imaginary particles a ray of light. A group of such particles travelling parallel (or al­most parallel) paths is called a beam of light.

Rays (and beams) of light are reflected from surfaces. The ray (or beam) which strikes a surface is called the incident ray while the ray leaving the surface is called reflected ray. Depending on the surface reflection may be regular or diffuse. Regular reflection occurs when light is reflected from a highly polished surface like a mirror, a metal plate, etc. The light reflected from a rough [глг] (грубый, шероховатый) surface is an example of diffuse reflection.

Geometrical optics accounts for a large amount of what we know about the phenomena of reflection from plane and curved mirrors. The distorted (искажать) forms we laugh at in those curved mirrors at the Fun House are accounted for by simple geometrical principles.

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