A Level Physics Practice Exam

The term "in phase" refers to points on the same side of the equilibrium position on a stationary wave. When points are in phase, they share the same displacement from the equilibrium position at any given instant. This means that if one point is at a maximum upward displacement, another point on the same side will also be at a maximum upward displacement at that same moment.

Points that are out of phase would exhibit opposite behavior—while one point is at a peak, another would be at a trough, which does not apply here. "Opposite phase" reinforces this concept as well, emphasizing the condition where points are not synchronized in their motion across the equilibrium position—they would be on opposite sides in this case.

Lastly, "at rest" does not accurately describe the relationship between points on a stationary wave, as it refers to a situation where no motion is occurring, rather than the specific phase relationship being discussed. Thus, the correct answer is indeed "in phase," highlighting the synchronized motion of points on the same side of the equilibrium position.