Given the path difference is Δx=47λ
Hence, the phase difference can be found as follows:
ϕ===λ2πΔxλ2π×47λ27π
The formula to calculate the intensity is given by
I=Imaxcos2(2ϕ)...(1)
From equation (1), it follows that
ImaxI======cos2(2ϕ)cos2(2×27π)cos2(47π)cos2(2π−4π)cos24π21