maximum phase difference between two waves

Thread Starter


Joined Apr 15, 2011

I believe the maximum phase difference possible between two waves is 90°. Suppose we have two waves. When the wave A is just starting out which means its phase is 0∏ or 2π, the wave B is at its 3∏/4 (correction: 3∏/2) phase. From wave A's perspective, wave B is lagging behind by 90° but from wave B's perspective the wave A is leading it by 90°. Would there be a difference mathematically? Perhaps, in one way, phase difference is 90° but in other way it's -90°. Please help me with it. Thanks.

Last edited:


Joined Oct 14, 2011
I think it is 180 degree.

Because the two waves could be in opposition of phase, then it is 180 degrees.

Check the attached example.



Joined Mar 6, 2009
This raises an interesting problem. Suppose you were looking at the two waves [A & B] on an oscilloscope - where they are time dependent sine functions with the same frequency.

What is the maximum phase difference you would be able to discern on the scope? As stevb & samin note, the maximum difference you could possibly see would be 180° when the two signals are in exact anti-phase.

Could you discern a difference of B leading A by 270°? Would it not simply appear to an observer that wave B leads A by 90°.

BTW PG1995: In your post you suggested a case situation where "..the wave B is at its 3∏/4 phase." Keep in mind that 3∏/4 is 135°.


Joined Feb 11, 2008
The maximum phase difference is 359.99 (repeating) degrees.
The maximum +/- phase difference is 180 degrees.