Question

Two points of differences between interference and diffraction

Answer 1

1. Two separate wave fronts originating from two coherent sources produce interference. Secondary wavelets originating from different parts of the same wave front constitute diffraction.
2. The region of minimum intensity is perfectly dark in interference. In diffraction they are not perfectly dark.
3. Width of the fringes is equal in interference. In diffraction they are never equal.
4. The intensity of all positions of maxima are of the same intensity in interference. In diffraction they do vary.
5. When we have two infinitely narrow slits separated by a distance apart near the source, we get interference. But when we have a single slit of finite width or rather an aperture near the source, we get diffraction