27. (a) What is the difference between interference
and diffraction of light ?
(b) What is wave front ? Give the types wavefront.
[P.T.O.
A-8540
Answers
(A)
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. Thus the two are entirely different in nature.
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.
(B)
A wavefront is a surface over which an optical wave has a constant phase. ... Such a surface which envelopes the particles that are in the same state of vibration is known as a wave front. The wave front at any instant is defined as the locus of all the particles of the medium which are in the same state of vibration.
Explanation:
Diffraction is the result of light propagation from distinct part of the same wavefront. While interference is the result of the interaction of light coming from two separate wavefronts. The width of the fringes in case of diffraction is not equal while the fringe width in case of interference is equal.