Two coherent point sources A and B emit in phase and are separated by 3.6λ. Considering only points lying strictly between the two sources on the line AB, how many points of minimum intensity occur?
Physics · Wave Optics · interferece of light and huygen principle
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Question

Two coherent point sources A and B emit in phase and are separated by 3.6λ. Considering only points lying strictly between the two sources on the line AB, how many points of minimum intensity occur?

G1 Physics · Accepted Answer

For minima, Δ = (n+1 ÷ 2)λ. The allowed positive path differences below 3.6λ are 0.5λ, 1.5λ, 2.5λ, 3.5λ. Each non-zero magnitude occurs at two symmetric points. Therefore, number of minima = 4×2 = 8. Hence the answer is 8.