(often referred to as 
or 
). The maxima of one disturbance then coincide with the minima of the other and vice versa, and the two oscillations or waves are totally out of step. [P6.1]
is: the condition in which two oscillations or waves of the same frequency have a phase difference of (often referred to as or ). The maxima of one disturbance then coincide with the minima of the other and vice versa, and the two oscillations or waves are totally out of step. [P6.1]
is equivalently: the condition of being totally out of phase. [P5.1]
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