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A slit of width a is illuminated by light of wavelength λ. The linear separation between 1^st and 3^rd minima in the diffraction pattern produced on a screen placed at a distance D from the slit system is ______.

Asked in JEE Main 4th April 1st Shift 2026 · Single slit diffraction

• (1) (Dλ)/a
• (2) 1.5(Dλ)/a
• (3) 2(Dλ)/a
• (4) 3(Dλ)/a

Step-by-step solution

Why the other options are wrong

• (1) Gives the spacing between adjacent minima, not the first and third.
• (2) Uses the maxima positions (n+1/2) in place of the minima, or halves the gap wrongly.
• (4) Takes the position of the third minimum from the centre instead of its distance from the first.

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