Water Waves:
An Exploration
By Craig Tyler, instructor
Diane Love, TA

You all know that astronauts and satellites travel in motions called "orbits". But did you know that ocean water can also travel in orbits?

Let’s set the stage. Your team names signify common types of waves:

Such pressure waves are longitudinal, which means that the direction of the wave’s oscillation is the same direction that the wave is traveling. For example, when you shout at someone ("look out, there’s sound waves headed right for you!"), the air expands and compresses along the same direction as the sound travels.

But, there is another sort of wave, which occurs at the interface between two media. These are transverse waves, which oscillate up and down, even though the wave is traveling side-to-side. The most common example is the water wave.

(If you have trouble picturing what longitudinal and transverse mean, don’t worry - you’ll see both in the Slinky lab.)

During our experimentation, we will investigate some of the physics of water waves:

  1. We will encounter lots of wave vocabulary, like diffraction, reflection, refraction, interference, wavelength, and amplitude. The really important thing to get out of all these words is that certain behaviors are common to all kinds of waves. For example, light waves interfere, causing bright and dark spots; but sound waves also interfere and create harmony, and when water waves interfere you can get either a really big wave or no wave at all (the same is true for waves in ropes and slinkys).
  2. We’ll explain the ordinary waves we see. Ocean waves generally form in deep water, where they travel as rolling waves. But in shallow water, they become crashing waves. We can watch this happen at the beach, as a rolling wave approaches shore, gets taller, and crashes. As the wave enters shallower water, it starts feeling bottom (that’s really the technical term for it), and friction against the ground slows the bottom of the wave down, so that the top of the wave crashes over it.
  3. We will also consider some special cases for water waves, like storms and rocks and tidal waves. We’ll see why understanding these waves can be important to us (especially in a boat!).
Everyone has seen water waves, but probably very few people really understand them. Since they are so common in our lives, we should take some time to know them better. Next time you’re bobbing up and down away from shore in Lake Michigan, think about why it is that the waves are traveling in toward the shore, but you aren’t.

WATER WAVES: An Exploration: Results

1

The following phenomena, Reflection, Diffraction, Refraction, and Interference, can be demonstrated for light waves, using lamps and mirrors and lasers, etc. Prove that these phenomena aren’t just for light, but for waves in general, by describing what they are and how water waves do them too.

WAVE

CHARACTERISTIC

DESCRIPTION

WATER

OBSERVATION

Reflection

 

 

Diffraction

 

 

Refraction

 

 

Interference

 

 

2

What happens when a wave hits a wall with a small gap in it? Draw a picture.

 

 

 

 

 

 

 

 

 

 

 

3

Describe the motion of some particular blob of water at the surface of the ocean as waves go by. Support your answer with specific results from an experiment you performed. Answer for both deep and shallow water. (Drawings may be used.)

AREA

MOTION DESCRIPTION

LAB OBSERVATION EVIDENCE

Shallow Water

 

 

Deep Water

 

 

4

Please offer a reason why some waves crash. Use an if/then format to frame your response.

 

 

 

 

5

If you were in a boat coasting down a river, and you saw a patch of water with small breaking waves, what would you do? Why?

 

 

 

 

6

Think about a tsunami. How is it created? Describe what it is like in deep water? In shallow water?

 

 

 

 

 

 

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