17.3 Laws of Reflection and Refraction of light on the basis of Wave Theory
Laws of reflection
As shown in Figure 2, the reflected wavefront has to be constructed as follows :
(i) From B as the center draw an arc of a circle of radius equal to distance DE.
(ii) From E draw the tangent EF to the arc.
(iii) E and F and all points between them are in phase as D & B all points between them are also in
a phase different from the first.
(iv) BFH and the parallel ray EG then are reflected rays.
Consider triangles BDE and BFE, then
Also, from the construction of the diagram it is obvious that the incident ray, the reflected ray and
the normal lie in the same plane (the plane of the diagram) and the incident ray, and the reflected ray are
on either sides of the normal. Thus, the laws of reflection are proved.
