On the basis of the following assumptions, Fresnel developed the theory of diffraction which explained the various diffraction effects. Assumptions: He assumed that:
(i) A wavefront can be divided into a large number of elements called Fresnel’s strips or zones whose are is very small.
(ii) Each element of wavefront sends secondary waves continuously.
(iii) The resultant effect at any point will be combination of the effect of all secondary waves reaching at that point.
(iv) The effect at any point due to a particular zone depends on
(a) the distance of point from ilie zone.
(b) the inclination of the point with reference to zone under consideration.
(c) area of the zone.