Center for Astrophysical Research in Antarctica
You all know that astronauts and satellites travel in motions
called "orbits". But did you know that ocean water
can also travel in orbits?
By Craig Tyler, instructor
Diane Love, TA
Lets set the stage. Your team names signify common
types of waves:
Such pressure waves are longitudinal, which means that
the direction of the waves oscillation is the same direction
that the wave is traveling. For example, when you shout at someone
("look out, theres sound waves headed right for
you!"), the air expands and compresses along the same
direction as the sound travels.
- The Rockets really should be spelled "rock it"s,
representing mechanical waves, or vibrations, like a
plucked guitar string. These waves propagate through solids.
- The Heat represents electromagnetic waves, like
light, heat waves, and x-rays. These EM waves can propagate
through empty space.
- The Sonics represent pressure waves, which are usually
associated with sound, as expansions and compressions push
forward through a medium like air or water (for example, perhaps
youve heard the sound of whales singing, or youve
heard of SONAR, by which submarines use underwater sound to
know when other submarines are near).
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, dont worry - youll see both in the Slinky lab.)
During our experimentation, we will investigate some of the physics
of water waves:
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 youre 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 arent.
- 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).
- Well 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 (thats 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.
- We will also consider some special cases for water waves, like
storms and rocks and tidal waves. Well see why understanding
these waves can be important to us (especially in a boat!).
WATER WAVES: An Exploration: Results
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
arent just for light, but for waves in general, by describing
what they are and how water waves do them too.
What happens when a wave hits a wall with a small gap in it?
Draw a picture.
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.)
LAB OBSERVATION EVIDENCE
Please offer a reason why some waves crash. Use an if/then
format to frame your response.
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?
Think about a tsunami. How is it created? Describe what it
is like in deep water? In shallow water?
[Education & Outreach]
[Search this Site]
[CARAweb Site Map]
CARA's research and education programs are supported in
part by the National Science Foundation under a cooperative
agreement, grant number NSF OPP 89-20223.
© Copyright 1998,1999,2000 by Center for Astrophysical Research in
Antarctica. This copyright applies to all web pages and
images created by CARA.
Questions? Comments? email us at firstname.lastname@example.org
Last modified Saturday, 11-Sep-1999 15:33:13 CDT