What is a Standing Wave?

12/05/2019

Standing waves, also known as stationary waves or seiche, are groups of waves that bounce up and down on a bounded or enclosed body of water. A standing wave results when two equal waves go in opposite directions. In this post, we will be talking about the properties of standing waves, as well as the science behind it. It’s very interesting to learn how nature works, allowing you to fully utilize your skills, especially when you encounter one of these when surfing. Now, let’s get on with the discussions.

What are Standing Waves?

Simply put, standing waves are the product of two propagating waves that travel in opposite directions. It is a combination of two opposite waves that have the exact same wavelength and amplitude. The intersection between the waves is referred to as nodes while the maximum amplitude’s positions are referred to as antinodes.

If you’re curious, you can easily observe the standing waves’ movement and behavior in laboratories. There are water tanks that are specially designed to allow scientists to produce the ripples artificially. To create an artificial stationary or standing wave, all you need to do is to transport a wave train across a bounded container against the walls. Then, you’ll be able to notice that the resulting wave is likely to superimpose the opposing waves; thus, doubling the water’s amplitude.

While the standing wave creates an optical illusion, the science behind it suggests that it only oscillates and does not move backward or forward. It can be especially difficult to notice standing waves in oceans and lakes, probably because of their longer wavelengths. However, if you have already familiarized yourself with their properties, you can now easily spot them in rivers, swimming pools, bays, and harbors.

As mentioned, these standing waves happen when there are two equal waves going in opposite directions, in which you get the regular up and down motion of the surface water, but waves don’t necessarily progress. These are especially common in areas where the waves reflect off seawalls or in breakwaters. Surprisingly, these are also very common in swimming pools.

A type of a standing wave is the seiche. If you want to observe how it happens, you may simply slosh around in your tub. If you feel less adventurous, try walking with a cup of coffee in your hand. Once you get a steady frequency, motion quickly builds up and the coffee is likely to slosh all over the place. This is especially true when designing harbors because extra care must be taken so that water that gets built up in seiches rather than getting sloshed up into the first floor of the buildings.

The Discovery of Standing Waves

Standing waves were first discovered and studied by Michael faraday in 1831. Faraday is an English scientist who first observed the formation of the stationary waves when he studied the liquid’s surface in a container that is vibrating. In 1890, Swiss hydrologist François-Alphonse Forel then pioneered scientific observations of these waves in Switzerland. It was called ‘seiche’, which is a Swiss-French expression, due to the swaying back and forth motion.

While standing waves are considered rare events in the oceans, these can be observed in the Adriatic Sea, the Baltic Sea, and in Japan. Also, seiches are likely to occur in lakes, mainly due to the local winds, as well as drastic alterations in the atmospheric pressure, earthquakes, and tsunamis. Sometimes, these occurrences may generate waves of over 15 feet.

Surfing and Standing Waves

Surfers seldom refer to the artificial stationary waves as standing waves. Even when these ripples don’t move and only stay in one place all the time, they do represent slightly different concepts. For instance, these indoor artificial waves are not necessarily standing waves, especially from a scientific perspective. Rather, these waves are often referred to as static waves. With this, you might not be able to surf a standing wave mainly because they never break and it’s inevitable that you and your surfboard will bounce up and down.

You might also wonder why surfing is good at some spots but lousy elsewhere. To be able to get a good understanding of this, you must first need to learn the mechanics as to how and why the waves break. Picture this, there are lots of upcoming waves headed to the beach. Those in front start to get dragged by the bottom which is why it slows down a bit. This is what allows the wave behind it to ride up the backs.

When the distance between the waves decreases, the energy then gets condensed into a narrow space and needs to go somewhere. This is the main reason why the wave gets taller. It’s also important to keep in mind that the energy goes around in an orbit just beneath the wave. These now taller waves will require bigger and stronger orbits. You can easily notice this because you get pushed onto the shore just behind where the waves break.

At the same time, the waves begin to slow down as they approach the shore and the orbit speed is now ahead of the wave’s speed. Here, the wave runs over itself. You may easily observe this, especially as the wave cresting. The water wouldn’t be able to support it so it breaks and when it releases all the wave’s energy, you get to propel your surfboard forward.

Conclusion

Now that we have reached the end of the discussions, we trust that you now know what a standing wave is. When you know what the specific properties of standing waves are, you can easily notice and observe them. Having such knowledge also allows you to further your surfing skills. If you know how and why water breaks, you get to have the perfect timing and momentum to surf towards the shore. With this informative article in mind, we do hope that you’ll also get to apply this new knowledge onto your next beach, lake, or river trip.

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