In Young’s double slit experiment, light from two identical sources are superimposing on a screen. The path difference between the two lights reaching at a point on the screen is 7λ/4. The ratio of intensity of fringe at this point with respect to the maximum intensity of the fringe is :
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Question

In Young’s double slit experiment, light from two identical sources are superimposing on a screen. The path difference between the two lights reaching at a point on the screen is 7λ/4. The ratio of intensity of fringe at this point with respect to the maximum intensity of the fringe is :

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G1 Physics · Accepted Answer

Δx = 7λ/4 ϕ = (2π/λ)Δx = (2π/λ) × 7λ/4 = 7π/2 I = I(max) cos²(ϕ/2) I/I(max) = cos²(7π/4) = cos²(2π – π/4) = cos²(π/4) = 1/2