Properties of Waves: Lesson for Kids

Instructor: Michelle Jones

Michelle has taught at the elementary level and has earned a master's degree.

What did one ocean say to the other ocean? just waved! Whether in the ocean or moving through the air through sound or light, all waves have certain properties. This lesson will explain some basic properties of waves.

Fun and Useful Waves

When Charlie visited the ocean with his family, he loved playing in the waves. As he stood in one spot and let the waves crash into him, he noticed that there was a pattern to the wave action. The water would rise up to a certain point, then fall back down. The distance between the waves seemed to be similar too. It reminded him of the seesaw he rides on the playground.

Ocean waves are easy to observe because we can see them. But when you hear a sound or see a light, you are also experiencing a different kind of wave action. To find out more about the properties of waves, Charlie decides to compare what he knows about them to how a seesaw works.

Crest and Trough

These two properties are actually opposites of each other. The crest is the highest point of the wave. The trough is the lowest point of the wave. Every complete wave cycle has one crest and one trough. When looking at an ocean wave, it is easy to spot the crest, but the trough is actually under the water.

As he looked at the waves, Charlie realized that when a seesaw is at the very top, right before it comes down, that's like the crest of a wave. Then, when it is all the way down at the ground, that would be considered the trough.

A complete wave cycle has one crest and one trough. Two cycles are shown here.
Diagram of wave crest and trough


Wave crests and troughs are necessary to measure the amplitude of a wave. Amplitude is the distance from a wave's crest to its resting position, the point in the wave where it is not moving any air or water. It can also be measured from a wave's trough to its resting position.

The resting position of a wave is similar to a seesaw when both sides are balanced and not moving up or down. Charlie decides to measure the amplitude of the seesaw when his friends are on it. He starts his measurement at the point when the seesaw is balanced, and ends it when one side is at the very bottom.

You can think of amplitude as half of the total wave height from crest to trough. The higher the wave moves up and down, the bigger the amplitude. Higher amplitudes result in more powerful ocean waves, louder sounds, and brighter light.

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