Two spherical waves with the same amplitude, A, and wavelength, , are spreading out from two point sources S1 and S2 along one side of a barrier. The two waves have the same phase at positions S1 and S2. The two waves are superimposed at a position P. (a) If the two waves interfere constructively at P what is the relationship between the path length difference (x = d2-d1) and the wavelength. (b) If the two waves interfere destructively at P, what is the relationship between the path length difference and the wavelength