Which two points on the wave shown in the diagram below are in phase with each other?

4. B and D

Explanation:

Two points along a transverse wave (such as the one in the figure) are said to be in phase when:

- the vertical position of the two points is the same

- The oscillation of the wave is going in the same way for both points

Basically, we say that two points are in phase when they are separated by a complete cycle (one complete oscillation) of the wave.

For this wave, we see that point B and C have same displacement, but they are not in phase since in B the oscillation is going down while in C is going up.

Instead, B and D are in phase, because they are separated by one complete cycle: both points have same displacement and the oscillation is going in the same way for both of them.

that tool is called an altimeter which measures your altitude which can be used to tell which atmosphere you are currently in, including the stratosphere.

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