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 \(n = 1, 2, 3, ...\)