Topic: Interference and Young's double-slit experiment· Optics

If the monochromatic source in Young's double slit experiment is replaced by white light, then

1. all bright fringes will be of equal width.

2. interference pattern will disappear.

3. there will be a central dark fringe surrounded by a few coloured fringes.

4. there will be a central bright white fringe surrounded by a few coloured fringes.

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Answer: 4. there will be a central bright white fringe surrounded by a few coloured fringes.

Key idea: Each colour makes its own fringe pattern, with fringe width \(\beta=\frac{\lambda D}{d}\).

At the centre the path difference is zero for every colour, so all colours give a bright fringe there and it appears white. Away from the centre the fringes of different colours separate (red is widest, violet is narrowest) and give a few coloured fringes, which soon overlap and wash out.

Option 4. The pattern does not disappear, the fringe widths are not equal, and the centre is bright, not dark.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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If the monochromatic source in Young's double slit experiment is replaced by white light, then

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