3.4.6　Analysis and questions

(1)Why should we keep the end surface of transmitter and receiver transducers parallel to each other in the resonance interference method?

(2)Why the end surfaces of the two transducers need to keep a small angle in the phase comparison method?(https://www.daowen.com)

(3)Why we suggest choosing straight line pattern as measurement standard in the phase comparison method?How much does the phase change from a positive straight line to a negative straight line?