Two identical water waves arrive at the same location with a phase difference of 3πrad. Which statement correctly characterizes the resulting interference?
a) Beats will be produced, because the constant phase difference causes the amplitude to vary in time.
b) Completely constructive, because 3π is a multiple of 2π.
c) Completely destructive, because 3π is an odd multiple of π.
d) Partially destructive, since cos(23π)=21, giving a non-zero resultant amplitude.