If a moving surface wave on water strikes a wall, it is found that another wave starts moving along the surface of water in the opposite direction. Again standing at a certain distance from a large wall if a loud sound is made, a similar sound comes back to our ears after a while. We know that if light falls on a mirror, it changes its direction. These phenomena are examples of the reflection of waves, although the nature of the waves is different in different cases.
We know that the direction along which the energy of a wave is transferred is called a ray. It is represented by an arrow-headed straight line. Suppose, a ray travels through a medium and is incident at a point on an interface with another medium. This point is called the point of incidence. The ray striking the interface is called the incident ray. The ray returning to the first medium from the point of incidence after reflection is called the reflected ray.
Law of Reflection:
Reflection of waves obeys two laws, these are known as the laws of reflection.
1. The incident ray, the reflected ray, and the normal to the reflector at the point of incidence lie on the same plane.
2. The angle of incidence is equal to the angle of reflection, i.e., i = r.