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In two separate Young's double-slit experimental set-ups and two monochromatic light sources of different wavelengths are used to get fringes of equal width. The ratios of the slits separations and that of the wavelengths of light used are 2:1 and 1:2 respectively. The corresponding ratio of the distances between the slits and the respective screens ((D₁)/(D₂)) is ______.

Asked in JEE Main 23rd Jan 1st Shift 2026 · Fringe width and fringe position

Answer: 4

Step-by-step solution

β = (λ D)/d is the same in both, so D ∝ d/λ.

(D₁)/(D₂) = (d₁)/(d₂)·(λ₂)/(λ₁) = 2×2 = 4.

→ 4

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