Microwaves are produced by two sources located at points X and Y. These two waves overlap at point Z. The diagram illustrates the routes taken by the two waves. The waves released from points X and Y are coherent. What direct effect does coherence between the two waves have?
- AThere is a constant difference in the path lengths $YZ$ and $XZ$.
- BThere is a constant difference in phase between the two waves at $Z$.
- CThere is a constant non-zero difference in frequency of the two waves at $Z$.
- DThere is a constant non-zero difference in amplitude of the two waves at $Z$.