In Young's double slit experiment, if the source of light changes from orange to blue then: (a) the central bright fringe will become a dark fringe. (b) the distance between consecutive fringes will decrease. (c) the distance between consecutive fringes will increases. (d) the intensity of the minima will increase.

Answer: (b). β ∝ λ and λblue < λorange, so fringe spacing decreases. The central fringe stays bright (zero path difference) and minima stay dark for equal slits. So the answer is (b).

In Young's double slit experiment, if the source of light changes… | JEE Main 2021 (27 Jul, Shift 1)

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YDSE: Fringe Width & Fringe Positions

In Young's double slit experiment, if the source of light changes from orange to blue then:

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Answer: (b)

$\beta \propto \lambda$ and $\lambda_{blue} < \lambda_{orange}$ , so fringe spacing decreases.
The central fringe stays bright (zero path difference) and minima stay dark for equal slits.
So the answer is (b).

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