Regular reflection:

1. When a beam of light (collection of parallel rays) falls on a smooth surface, it gets reflected. after reflection, the reflected rays will be parallel to each other.

2. Here, the angle of incidence and the angle of reflection of each ray will be equal.

3. Hence, the law of reflection is obeyed in this case and thus a clear image is formed.

4. This reflection is called 'regular reflection' or 'specular reflection'.

Example : Reflection of light by a plane mirror and reflection of light from the surface of still water. 

Irregular reflection: 

1. In the case of a body having a rough or irregular surface, each region of the surface is inclined at different angles. 

2. When light falls on such a surface, the light rays are reflected at different angles. In this case, the angle of incidence and the angle of reflection of each ray are not equal.

3. Hence, the law of reflection is not obeyed in this case and thus the image is not clear. Such a reflection is called ‘irregular reflection’ or ‘diffused reflection’.

Example : Reflection of light from a wall.