## Sunday, 11 December 2016

### GEOMETRICAL OPTICS - BASIC CONCEPTS

INTRODUCTION:

What is light? Light is the energy emitted by the excited atoms which can cause the sensation of vision in a human eye, hence light is a form of radiant energy.

What is optics? The branch of physics which deals with the phenomena concerning light is called optics .

We can classify the optics into : 1) Geometrical optics 2) Physical optics.

What is Geometrical optics? The study involves, the light is considered as moving along a straight line as moving along straight line as a ray. A ray of light gives the direction of light. When the light meets a surface which separates two media, reflection and refraction take place.

What is Physical optics? Physical optics deals with the theories of light and explains all the phenomena such as reflection, refraction, interference, diffraction, polarisation, and rectilinear propagation.

Definitions:

a) a ray: A ray is nothing but, the path along which light travels is called a ray.

b) a beam: A bundle of rays is called a beam.

c) a pencil: A narrow beam is called a pencil of light

types of objects:

REAL OBJECTS: From a point, if two or more incident rays actually emanate or seem to emanate.

VIRTUAL OBJECT: If the rays are intercepted by an optical element, then the point of convergence is a virtual point behind the optical element.

In general, we can say that an object is real when two rays emanate or diverge from a point, and an object is virtual when two incident rays seem to converge to that point