Three coherent sources S₁, S₂ and S₃ each produce intensity I₀ at P. With S₁ and S₂ on, intensity at P is 2I₀; with S₂ and S₃ on, it is also 2I₀. Select the correct possibilities.
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Question

Three coherent sources S₁, S₂ and S₃ each produce intensity I₀ at P. With S₁ and S₂ on, intensity at P is 2I₀; with S₂ and S₃ on, it is also 2I₀. Select the correct possibilities.

G1 Physics · Accepted Answer

Step 1: Add the waves as phasors. For two amplitudes A₁,A₂ with phase difference φ, A² = A₁² + A₂² + 2A₁A₂ cosφ. Step 2: Intensity is proportional to A²; constructive/destructive conditions are Δ = nλ and Δ = (n+½)λ. Step 3: Apply the stated phases/path differences. Final: B: When S₁ and S₃ are switched on simultaneously, intensity at point P can be 0; C: When all 3 sources are switched on simultaneously, intensity at point P can be I₀.