Hi, I have a question about destructive interference. Suppose I have two very closely spaced EM sources, e.g two RF emitters. At a point far away from the sources the arbitrarily orientated magnetic field due to source one is: B1(t)=sin(ωt) and source two: B2(t)=sin(ωt+pi) so the total field is null due to destructive interference B(t)=B1(t)+B2(t)→0 (the same is true for the electric fields). Is there anyway to extract energy from the nonzero energy wound up in the individual fields? Or does destructive interference of the two fields make this impossible?