Reflection of light on Rough surfaces

 

As we look at the rough surface, we find that it has lots of heaps and bumps. They contain several curved surfaces. Any curved path of the surface must be a part of a circle and must be having a centre as well that is called the centre of curvature. We also know that- To obtain the reflected ray, we need a normal line with respect to which the angle of reflection is calculated. So we need to determine the angle of reflection.

But how to do that?

let's learn now.

1. Draw a tangent at the point of incidence.
2. Now, if we join the point of incidence and the centre we get a line which is perpendicular to the tangent. This line can be considered as the normal line.
3. Now as we have got the normal line. According to the angle of incidence, the angle of reflection can be calculated (as the law of reflection says, Angle of incidence is equal to the angle of reflection) and accordingly we can draw the reflected ray. So in case of rough surfaces what happens is that there are a lot of curves where the centre of curvatures do not coincide and thus the orientation of the normal is different for each point of incidence and consequently we get different angle of reflection  for the parallel incident rays, which we see as an irregular reflection.