Light is a form of energy. Light helps us to see object .But it is not visible to us. We can define light as the form of energy which causes in us the sensation of sight. Light always travels from one point to another in straight lines. The light rays travel from one point to another in the form of waves. Light is an electromagnetic wave in nature as it requires a material medium for its propagation .As we have discussed that Light is an electromagnetic wave so its propagation from one point to another depends on the nature of medium through which it passes. That is why the speed of light is very high being 3 × 108 meters per second but the speed of light is less in water and glass as compared to speed in vacuum (or air ).
A light wave which travels from one point to another in a straight line path joining them is called a ray of light while a bundle of such rays is called a beam of light.
When a ray of light falls on a polished and shining surface of an object, then it is sent back in the same medium. The process of sending back the light rays after falling on the shining surface of an object is called reflection of light.
Laws of Reflection of Light
There are two laws of reflection of light which are applicable both in the reflection of light from the plant mirrors or from spherical mirrors. These are:
1. The angle of incidence is always equal to the angle of reflection. i.e. i = r
It means that during the reflection of light if the angle of incidence is 25 degree then the angle of reflection will also be 25 degree . And if the angle of incidence is 60 degree then the angle of reflection will also be 60 degree.
2. The incident ray, the normal at the point of incidence of mirror and the reflected ray, all lie in the same plane.