Figure 35.3 shows the wave pattern produced by two identical, coherent sources emitting waves with wavelength and

Figure 35.3 shows the wave pattern produced by two identical, coherent sources emitting waves with wavelength λ and separated by a distance d = 4λ.
(a) Explain why the positive y-axis above S1, constitutes an anti nodal curve with m = +4 and why the negative y-axis below S2 constitutes an anti nodal curve with m = -4.
(b) Drew the wave pattern produced when the separation between the sources is reduced to 3 λ. In your drawing, sketch all anti nodal curves-that is, the curves on which r2 – r1 = m λ. Label each curve by its value of m.
(c) In general, what determines the maximum (most positive) and minimum (most negative) values of the integer m that labels the anti nodal lines?
(d) Suppose the separation between the sources is increased to 7½ λ. How many anti nodal curves will there be? To what values of m do they correspond? Explain your reasoning. (You should not have to make a drawing to answer these questions.)