Wave Optics question for NEET (NEET 2024), with solution

Answer: (A) there will be a central bright white fringe surrounded by a few coloured fringes.

At the centre the path difference is zero for every wavelength, so all colours interfere constructively there and the central fringe is white.

Away from the centre, the fringe positions depend on wavelength (fringe width $\beta = \dfrac{\lambda D}{d}$), so the colours separate into a few coloured fringes. Further out they overlap and the pattern washes out to uniform white.

Solution by Sreeraj P, M.Sc Physics