Practice portal › Wave Optics › Interference and Young's Double Slit Experiment
Asked in GUJCET 2018 · Intensity and coherent sources
Idea: interference and diffraction are told apart by where the superposing waves come from.
Interference fringes are the superposition of two complete wavefronts from two coherent sources, so they need coherent sources, they are evenly spaced, and every bright fringe carries the same intensity.
Diffraction fringes are the superposition of secondary wavelets from different parts of one and the same wavefront, and that is what 'a limited portion of a wavefront' describes.
So equal brightness, constant spacing and coherent sources are all correct statements about interference fringes.
The wrong statement is that the fringes are due to a limited portion of a wavefront, which is the origin of diffraction fringes instead.
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