Louisiana State University
PHYS 2111
From The Physics Classroom's Physics Interactives http://www.physicsclassroom.com
©The Physics Classroom, All Rights Reserved This document should NOT appear on other websites.
Exploring Waves
Purpose:
To explore a few simple characteristics of waves traveling along a rope and sound waves traveling
through air.
Getting
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From The Physics Classroom's Physics Interactives http://www.physicsclassroom.com
©The Physics Classroom, All Rights Reserved This document should NOT appear on other websites.
Exploring Waves
Purpose:
To explore a few simple characteristics of waves traveling along a rope and sound waves traveling
through air.
Getting Ready:
Navigate to the Simple Wave Simulator Interactive at The Physics Classroom website:
http://www.physicsclassroom.com/Physics-Interactives/Waves-and-Sound/Simple-Wave-Simulator
Navigational Path:
www.physicsclassroom.com ==> Physics Interactives ==> Waves and Sound ==> Simple Wave Simulator
Getting Acquainted:
Once you've launched the Interactive and resized it, experiment with the interface. Tap on the Slow
Motion, Real Time, and Fast Motion tabs at the top of the interface to observe how to control the
tempo of the animation. Toggle back and forth between a sound wave and a rope wave by tapping on
the Show Wave as ... button. Finally, observe the sliders at the bottom of the interface for controlling
the Frequency, Wave Speed, and Wave Amplitude.
Exploring Waves on a Rope
Set the animation to Show Waves on a Rope using a Real Time tempo and Frequency, Wave
Speed, and Wave Amplitude values of 0.10 Hz (approximately), 100 cm/s, and 2 cm respectively.
Then use the controls on the animation to answer the following questions.
1. In Physics, we distinguish between wave motion and particle motion. Wave motion refers to
the movement of a wave-like pattern from one location on the medium to another. When you
view a water wave moving along the surface of water, you are observing wave motion. There is
a very obvious movement of a collection of crests and troughs along the water surface. In the
Simple Wave Simulator, there is a collection of crests and troughs moving through a rope; this is
wave motion. But there are also three points on the rope that are colored red. When you observe
the motion of these points, you are observing particle motion - the motion of particles of the
rope. Describe the motion of these particles.
2. If you observe closely, you will notice that the particles leave a trail behind them as they move.
The longer the trail, the faster that the particle is moving. During any up-and-down cycle of the
particle, does it move with a constant speed or with a changing speed? If the speed is changing,
at what point during its motion does it move with the greatest speed? the smallest speed?
Discuss fully.
From The Physics Classroom's Physics Interactives http://www.physicsclassroom.com
©The Physics Classroom, All Rights Reserved This document should NOT appear on other websites.
3. There are a variety of ways to categorize waves. One way is to categorize waves as being
transverse waves, longitudinal waves, or surface waves. Waves in each of these categories differ
from one another in terms of how the direction of the particle motion compares to the direction
of the wave motion. The waves traveling through the rope are transverse waves. For transverse
waves, compare the direction that the particles move to the direction that the wave moves?
4. Now use the Frequency slider to increase the frequency to a high value. Compare the motion of
the particles when the frequency is high to the low-frequency motion. How would you describe
the difference?
5. This next step is going to take some skill and some careful observation. The wave speed is
associated with the movement of crests and troughs along the medium. Faster waves will have
crests that move from the left side of the screen to the right side of the screen in less time; that is
the crests move from left to right faster. Set the animation to a low frequency (about 0.1 Hz) and
observe the wave speed. It might help to put your finger or a pen cap on a crest and follow move
your finger (or pen cap) from left to right along with the crest. Then repeat for a high frequency
(about 1.0 Hz). Make the same observation of wave speed - the speed of the crest moving from
let to right across the screen. Does this ten-fold increase in frequency - from about 0.1 Hz to
about 1.0 Hz - have any noticeable and appreciable effect upon the wave speed? Explain your
answer and discuss your observations.
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