Figure 1 shows two point sources S1 and S2 that emit sound of wavelength l  2.00 m. The emissions are isotropic and in phase, and the separation between the sources is d  16.0 m. At any point P on the x axis, the wave from S1 and the wave from S2 interfere. When P is very far away (x=infinite), what are (a) the phase difference between the arriving waves from S1 and S2 and (b) the type of interference they produce? Now move point P along the x axis toward S1. (c) Does the phase difference between the waves increase or decrease? At what distance x do the waves have a phase difference of (d) 0.50l, (e) 1.00l, and (f ) 1.50l?