Physics question phase difference

Hi, please could i have help on this question? I thought the phase difference would be 135 degrees but it’s 180 and I don’t understand how?
Here is the question: https://app.gemoo.com/share/image-annotation/637748729958240256?codeId=vJ3kNVAEz2Yp5&origin=imageurlgenerator

Thank you!

Reply 1

lordaxil

Since the wave is stationary, each point on either side of a node is vibrating in anti-phase. In other words, as P is going up, Q is going down, and vice versa. The amplitude of the vibrations, or the horizontal distance between P and Q, is irrelevant here.