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Asked in GUJCET 2014 · Fringe width and fringe position
Given: the width of the fourth bright fringe is 2×10⁻² cm.
Idea: fringe width means the separation of consecutive bright fringes, β=(λ D)/d.
Nothing on the right-hand side depends on the order n, so in a Young's pattern all the fringes are equally wide.
The sixth bright fringe is therefore exactly as wide as the fourth.
Width =2×10⁻² cm.
What does grow with the order is the distance of the fringe from the centre, yₙ=nβ, and that is the quantity the question is inviting you to compute by mistake.
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