Lab: Waves on a String
http://phet.colorado.edu/simulations/sims.php?sim=Wave_on_a_String
(or google “phet”, go to Colorado site, click on “play with sims”, click on “waves on a string”)
Objective: Students will be able to discuss wave properties using common vocabulary and they will
be able to predict the behavior of waves through varying medium and at reflective endpoints.
Background: Complete the steps below. Each of you should be at a computer and making your
own observations but you will be discussing ideas with a partner. (All of your answers and notes
in this part is your background research in your lab book. You may use bullets, lists, etc to organize
the information.)
PART I
1. Click “Run Now” to start the Waves on a String simulation. Spend a few minutes investigating
wave behavior using the simulation. As you look at the waves’ behavior, make careful
observations and discuss some of the characteristics that you observe.
2. On your whiteboard, summarize a list of characteristics that you will use in this activity to
describe the waves. Be prepared to share your observations with the rest of the class.
3. Describe each characteristic in words that any person could understand (be specific). Leave
some writing space for characteristics that you might think of later during the activity.
PART II
4. With the Oscillate button on and with No End checked, investigate waves more carefully
using the Amplitude slider. Write answers to the following after you have discussed them with
your group and come to an agreement.
a) Define Amplitude in everyday language.
b) Explain how the wave behaves as the Amplitude changes using the characteristics you
described in #2
c) What kinds of things might affect the Amplitude of a wave? Explain your idea in terms of
real life experience (sound, earthquakes, electronics, light?). Use real situations!
5. Repeat step number 4 (including a-c), for Frequency, Tension and Damping.
You should now have a pretty good working knowledge of the parts of a wave and terminology to
describe wave behavior.
Procedure (you may write “see handout” in this section of your lab book): (All of your answers
and notes here is included in your DATA section in your lab book)
1. Set Amplitude, Frequency and Tension on high, Damping on low. Also, have on Oscillate, Timer
and No End. Use the Pause button to freeze the wave.
a) Place a blank piece of paper on your monitor and trace the wave and the wave generator.
Mark the green dots. This is a vertical position- horizontal position graph, label each axis
clearly.
b) With the simulation Paused, press the Step button. Use the same piece of paper and trace
the new wave. Make sure to get the generator in the same spot. Be sure to note where the
green dot is during each step. Do this at least four times.
c) Describe the differences and similarities in the characteristics of the wave each time. You
may have to do some more tests by pressing Play, then Pause and tracing to test your ideas.
d) What did you notice about the motion of the green dots? Be sure to include how their
location changes over time.
2. Set Amplitude, Frequency and tension on high, Damping on low. Also, have on Oscillate, Timer
and No End. Use the Pause button to freeze the wave.
a) Make a data table to record the vertical position of the green ball versus time.
b) Measure the vertical location of a green ball using the Rulers tool in the upper right hand
corner of the simulation window.
c) Record the vertical position and time.
d) With the simulation paused, press the STEP button and record the new position and time.
Continue this process until you have at least 25 data points.
e) Open an Excel spreadsheet. Label columns appropriately and enter the time and position
data recorded above.
f) Use Excel to create a Graph of vertical position verses time. Label your axis. Print the
graph and tape it into your lab notebook.
3. Investigate how waves behave when the string end is Fixed and Loose with Manual settings.
Discuss the behavior with your partners. Test your ideas and the write a summary.
4. Google standing wave. Investigate how to produce one with the simulation. Write directions
on how to use the simulation so that anyone could produce a standing wave on this website.
Data:
Your data should include
 all observations during the simulation (use appropriate vocabulary)
 traced graph #1 (vertical vs. horizontal position with green dots)
 table (meeting scientific specifications) with green dot position and time
 graph #2 (vertical position vs. time with green dots)
Analysis:
1. Summarize the differences and similarities between a vertical position- horizontal position
graph (the first graph you drew) and a vertical position-time graph (the second graph you
drew). Use the characteristics you developed in your background investigation. Be specific to
what information each graph displays and note the fundamental differences.
Conclusion/Reflection:
1. Briefly describe several characteristics of a wave using correct scientific vocabulary.
2. How do waves behave differently with an open end, fixed end or loose end? Be specific.
3. If I see my favorite rubber duckie floating in a pool with wavy water, can I just wait a few
moments and have the waves deliver it to me? Explain.
4. Describe two situations in your life that waves matter and why? Be eloquent, clever and
specific.