Wavelength, Speed, and Frequency

Use a virtual simulation to explore the relationship between wave speed, wave frequency, and wavelength. To access this activity, please visit: https://phet.colorado.edu/. Search Waves on a String (HTML5). Click Play.

Experiment 1

• Click on "oscillate" to produce a continuous stream of pulses.
• Check the "rulers" box (you can click and drag the rulers).
• Click on "No End" and set the tension to "high" and "damping" to zero. Do not change the amplitude or tension settings during this experiment.

Procedure:

1. Set the amplitude for all trials at the same value.Record this value: _______ cm.
2. For five different frequencies (of your choosing), use the ruler to measure the wavelengths of the resulting waves. Record the frequencies and wavelengths in Table 1. (Hint: Pause the simulation to make measuring easier.)
3. Wave speed is the product of frequency and wavelength (wave speed = frequency * wavelength). Calculate the wave speed for each trial and record these values in the table.

Frequency (Hz)	Wavelength (cm)	Speed (cm/s)

Table 1

Questions:

1. In your own words, what is wave frequency?

2. Refer to your data. What is the relationship between frequency and wavelength? In other words, as frequency increases (or decreases), what does wavelength do?

3. How did the wave speed for all your trials compare?

4. If the amplitude had changed for each trial, do you think you would have observed the same results? Why or why not?

Experiment 2

Repeat the procedure from Experiment 1 but use a different amplitude for each trial. Record this value: _______ cm.

Be sure to use the SAME wave frequencies that you used in Experiment 1. Record all data in Table 2.

Frequency (Hz)	Wavelength (cm)	Speed (cm/s)

Table 2

Questions:

5. When you changed the amplitude, what part of the wave changed? (You may want to run the wave in slow motion as you slide the amplitude setting up and down.)

6. Summarize your results. How does amplitude affect wave speed?

The green dots are reference points on the string. Step through a simulation and observe the relative movement of the green dots.

7. Based on your readings from the text (or other source), what is the difference in wave motion between a longitudinal wave and a transverse wave?

8. Describe the motion of the green dots. Do they change position in the horizontal direction? How about in the vertical direction? What type of wave is it? (Hint: Refer to your response for question (6).