What is Rayleigh's criterion? .

Explanation

(i) According to Rayleigh's criterion, for two point objects to be just resolved, the minimum distance between their diffraction images must be in such a way that the central maximum of one coincides with the first minimum of the other and vice versa.
(ii) Such an image is said to be just resolved image of the object. The Rayleigh's criterion is said to be limit of resolution.