1. Rays reflected from the smooth surface are parallel to one another.
Reflection of light from a smooth and a rough surface
2.When the reflecting surface is plane and smooth, the angles of incidence (i) as well as of reflection (r) are the same for all parallel rays incident on the surface. If i1, i2, i3, … are the angles of incidence for incident parallel rays, and r1 , r2 , r3 , …, are the corresponding angles of reflection, then, i1 = i2 = i3 = ……. = r1 = r2 = r3 = ….. This is called regular reflection. Here, the reflected rays are parallel to one another. If the reflecting surface is rough and parallel rays are incident on it, then the angles of incidence are not equal and hence the angles of reflection are also not equal. Here, i1 ≠ i2 ≠ i3 … and r1 ≠ r2 ≠ r3 …, but r1 = i1 , r2 = i2 , r3 = i3 … as laws of reflection are obeyed. This is called irregular reflection. [Fig.(b)]. Here, the reflected rays are not parallel to one another and spread over a large surface.