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Describing a Wave

Measure and Compare Amplitude

Review the diagram below on the left. Then look at the picture to the right. Notice that amplitude can be measured two ways—from the resting position to the peak and from the resting position to the trough.

Describing a Wave
A labeled diagram of waves.
A line cuts across the middle of an up and down shape of a curvy line that represents waves. The line that cuts across the middle is called “the resting position.” The top part of a wave is called the peak. The bottom part of the wave is called the trough. The amplitude of one wave is shown as the distance from the line that cuts across the middle to the top of one wave, or peak. Amplitude is also measured from the middle resting position to the bottom of one wave, or the trough. The distance from resting position to peak is equal to the distance from resting position to trough.

Measuring Amplitude on a Rope
A labeled diagram of a child making waves with a rope that is tied to a tree.
A dotted line cuts across the middle of the waves to show the resting position. The amplitude from the resting position to the peak, or top of the wave, measures two feet. The amplitude from the resting position to the trough, or bottom of the waves, also measures two feet.

Compare Waves

Click the Arrange It button on the right to get started.

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