Two coherent point sources \(S_1\) and \(S_2\) emit waves of wavelength \(\lambda\). The waves interfere constructively at point \(P\). Which equation correctly represents the condition for constructive interference at \(P\)? (path difference = \(|S_1P – S_2P|\))

• A

  path difference = \(n\lambda\) where \(n\) = 0, 1, 2, ...

• B

  path difference = \((n+\frac{1}{2})\lambda\) where \(n\) = 0, 1, 2, ...

• C

  path difference = \(n\lambda\) where \(n\) = 1, 2, 3, ...

• D

  path difference = \((n+\frac{1}{2})\lambda\) where \(n\) = 1, 2, 3, ...