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Question:

Interference pattern is observed at 'P' due to superimposition of two waves coming out from a source 'S' as shown in the figure. The value of 'l' for which maxima is obtained at 'P' is (R is perfect reflecting surface)

l=(2nλ)2(√3)

l=(2nλ)√34(2-√3)

l=2nλ√3

l=(2nλ)√3

Solution:

Path difference=2Lsec30°
2L = 2L(2√3)
Δx=2L√3(2-√3) (1)
Phase difference=2πλ×Δx+x. (2)
For maxima,Phase difference=2nπ (3)
By solving the numbered equations, we get
l=(2nλ)√34(2-√3)