PhET: Sound Waves Lab Name: Period: Date:
Directions: Follow the steps below while using Wave Interference. Be sure to completely answer each question.
1. Do a search for Phet Wave Interference. Click where it says Waves on the left.
2. On the next screen click the speaker symbol on the left.
3. Click the box next to Play Tone
4. Click the green circle on the speaker on the left to start the simulation.
a. You should hear a constant sound if your sound is on. Move the frequency button to the left and
right. Describe what happens to the sound as you move from minimum to maximum frequency.
Minimum frequency = low pitch. Maximum frequency = high pitch.
b. Does the change of sound and frequency match what was described in our notes? Explain how it
does or does not.
Yes. Low frequency = low pitch and high frequency = high pitch.
5. Turn the sound off and move the frequency to maximum. Observe the waves produced. Now switch to
minimum frequency.
c. What characteristic of the wave changes, other than frequency. (Look at the spaces between the
waves.)
Space between waves or wavelength.
a. If you have trouble seeing the relationship in the question c switch to the water wave
view, then click Side View on the lower left side of the screen. Switch between
minimum and maximum frequency to see the relationship.
6. Switch back to the speaker sound setting. Click the Particles button on the right. Compare the
red air particles on the left side of screen to the red particles on the right.
d. What is different about the behaviors of the particles on opposite sides of the screen?
Particles on the left move more than the particles on the right.
e. What characteristic of a wave does the difference in movement of the red particles represent?
The distance of displacement from rest position is measured by amplitude.
a. If you can’t see the characteristic in question e click Graph on the right side of the screen.
This converts the compression wave to a transverse wave. (The dotted line on the graph
indicates the rest position of the medium.)
7. As our notes from last week mention the loudness or intensity of sound (similar measures but not exactly
the same) are both related to the amplitude of the wave.
f. When you hear a sound, what is typically true about the loudness / intensity of the sound the
closer you get to the source?
The closer you are to a sound’s source the louder or more intense the sound.
g. How does the amplitude of the waves on the screen match the loudness / intensity as you get
closer to the speaker on the left?
The amplitude or movement of the particles increases as you get closer to speaker.
8. Next, click the green button on the speaker on the left to stop the sound. Let the particles in the medium
settle down, then click the green button again to turn on the speaker. Notice what the yellow part of the
speaker is doing to create the sound.
