If you’ve ever spent some time near a body of water, then you noticed that on a calm day there are very few waves in the water, and on a windy or stormy day there are many waves. This, of course, explains what causes waves in the water.
It is the wind. A wave is a way in which some form of energy is moved from one place to another. Some sort of force or energy must start a wave, and the wind provides that energy in the water.
When you watch the waves move, one after the other, the water seems to move forward. But if there is a piece of floating wood in the water, it will not move forward as the waves seem to do.
It will only bob up and down with the waves. It moves only when the wind or tide moves it. Then what kind of motion is taking place in a wave? A water wave is mostly the up-and-down movement of water particles.
The movement passes on toward the shore, but not the particles of water. For example, if you have a rope you can send a kind of wave along the rope. The up-and-down movement passes along the rope, but not the particles of the rope.
As the bottom of a water wave strikes the ground a short distance from the beach, it slows up because of friction. The top keeps going, and then topples over, and thus forms a breaker.
The energy that formed the waves loses itself against the shoreline. All you have to do is stand among the waves along a beach and you’ll soon find out that they have energy!
In a water wave, the water particles move in a circular path, up and forward, as they are pushed by the wind. Then they move down and back as gravity draws the heaped-up water back to a common level.
These up-and-down movements carry the wave along. The distance from crest to crest of a wave is the wavelength, and the low point is called the trough.