The line-width of a bright fringe is sometimes defined as the separation between the points on the two sides of the central line where the intensity falls to half the maximum. Find the line-width of a bright fringe in a Young’s double slit experiment in terms of λ, d and D where the symbols have their usual meanings.
Simran Bhatia , 11 Years ago
Grade 11
1 Answers
Aditi Chauhan
Last Activity: 11 Years ago
Sol. i) When intensity is half the maximum l/l base max = 1/2
⇒ 4a^2 cos^2(∅/2)/4a^2 = 1/4
⇒ cos^2 (∅/2) = 1/4 ⇒ cos(∅/2) = 1/2
⇒ ∅/2 = π/3 ⇒ ∅ = 2π/3
⇒ Path difference, * = λ/3
⇒ y = xD/d = λD/3d
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