Introduction

Light is form of energy which causes sensation of sight in us to see the things around us. We see objects around us by or eyes, but eyes alone can not see the objects. We need a light source to see the objects.

Light coming from an object enters in our eyes that we are able to see that object. Light may be emitted by the object itself or object reflecting the light falling on it from other source.

Example: Sun is visible because of its own light and moon is visible because of light reflected by moon which is falling on it from the sun.

Objects which emit their own light are called Luminous Objects. Examples are sun, stars, bulb, bulbs etc.

Objects which do not emit light themselves are called Non-Luminous Objects. Examples are human, animal, furniture etc.

Light travels is a straight line and hence we see shadow of an object when light falls on it from any light source.