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By the time the wave reaches B from A the phase of vibration of A has changed. The difference between the states of vibration of A and B is called phase difference (ΔO).

From this wave motion, if we consider any two consecutive crests c₁ and c₂, the path difference between them is λ, the time difference is T and the phase difference is 2π.

A path difference of (λ) corresponds to a phase difference of 2π, thus, a path difference (x) corresponds to the phase difference 2πr/λ.

Δϕ = (2πx)/λ = 2π/λ (path difference)

By increasing angle length of the wave is decreasing and vice versa by decreasing angle, length of the wave is increasing.