Waves out in the ocean, as opposed to those washing up onto the beach, are waves in the physics sense. To the contrary, it’s a motion of matter from one location to the next. A physicist would say that the water crawling over the beach is not a wave in the physics sense because it’s not a transfer of motion or energy from one location to the next. The molecules are moving from one place to another, not jiggling in place and communicating their motion to a neighbor. Yes, we call those tumbling, foaming things “waves.” But they don’t fit the physics definition of “waves.” The water molecules are rushing, let’s say, 30 feet up onto the sand. Follow the oscillation of one of the red dots on the wave surface. Another example of a mix of flows and waves is the surf rolling in. In addition, waves, where water molecules are oscillating, ruffle the surface of the water.Īnimation of a deep ocean wave. The accompanying photo of a canoe being paddled downstream illustrates a flow of matter-the canoe and the water are flowing downstream. So, rivers include both flows of water, where the molecules are moving downstream, and waves, where they are oscillating. Of course, a river also includes actual waves in the physics sense, where water molecules are instigating motion in each other. They are not staying in the same location and communicating motion to a neighboring molecule. ![]() The water molecules are moving downstream. You’re watching the water molecules, bits of matter, flowing in a direction. When you’re standing on a river bank watching water rush downstream, you’re not watching a wave. Repeating myself here-a wave, as defined in physics, is not the moving of an object from one place to another. The flow of the water bears a canoe downstream. Motion is directed energy, so a wave is also a transfer of energy through a medium. In brief, a wave is a transfer of motion through a medium. The neighboring particle then pushes or pulls on the next, and so on. Of course, a physical wave doesn’t involve a mental connection it involves a physical push or pull on the neighboring particle. In a physical wave, a particular motion, an oscillation, is communicated from one bit to the next bit of some medium. The stadium wave is a good metaphor for a physical wave. Each person has decided that when my neighbor stands and then starts to sit, I’ll stand up. The up/down/up motion is called an “ oscillation.” Unlike in physics, the people aren’t physically making each other stand-it’s a mental connection. But something is moving around the stadium-a motion-up and then down. The people aren’t moving their bodies down the bench–they each sit down again in exactly the same seat. Wave in a stadium crowd, a metaphor for a physical wave. Click for animation. Each person or group stands and inspires their neighbor to stand. ![]() A wave that travels through the crowd in a football stadium is a good metaphor for a wave in physics. ![]() In a wave, a motion of one particle instigates the same motion in a neighboring particle. The accompanying animation demonstrates the motion of a seismic wave, the wave created by an earthquake, traveling through the Earth.Ĭlick on image to see animation of a wave. A wave is a movement that propagates through a medium.
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