Waves are hard to teach from a textbook because they move. The free PhET simulation Wave on a String lets students wiggle the end of a string and change amplitude, frequency, damping and tension while watching what happens. This PhET Wave on a String lab turns the simulation into a structured 50-minute lesson for grades 8–12.
In this guide8 sections
Lab at a glance
- Grade level: 8–12 physical science or physics
- Time: 45–55 minutes
- Objectives: describe amplitude, frequency and wavelength; explain how frequency affects wavelength; describe how tension affects wave speed.
- Materials: device with the free PhET simulation, worksheet
Know the simulation
- Modes: Manual (drag the wrench), Oscillate (continuous wave) and Pulse (single pulse).
- End options: Fixed End, Loose End and No End.
- Sliders: amplitude, frequency, damping and tension.
- Tools: rulers, a timer and a reference line, plus slow motion and pause.
Step-by-step lesson plan
- Hook (5 min). Ask: “If you shake a rope faster, do the waves get longer or shorter?” Students predict.
- Free exploration (8 min). Students try every mode and end option and note one surprise.
- Part A: amplitude (8 min). Oscillate mode, No End, damping at zero. Change amplitude and measure wave height with the ruler.
- Part B: frequency and wavelength (12 min). Keep amplitude constant. Measure wavelength at three frequencies and record in a table.
- Part C: tension and speed (10 min). Use Pulse mode and the timer to compare how fast a pulse travels at low and high tension.
- Part D: reflection (5 min). Compare a pulse hitting a fixed end with one hitting a loose end.
- Exit ticket (4 min). “Explain why increasing frequency changes wavelength.”
Worksheet questions
- What happens to the wave when you increase amplitude? What stays the same?
- Complete the table: frequency vs. measured wavelength. What pattern do you see?
- When tension increases, does the pulse travel faster or slower?
- Describe the reflected pulse at a fixed end and at a loose end. How are they different?
- What does damping do to the wave over time? Give a real-world example.
- Use v = f × λ to explain your frequency results.
Answer guide
| Question | Expected answer |
|---|---|
| Amplitude | Waves get taller; wavelength and speed stay the same. |
| Frequency | Higher frequency gives shorter wavelength when tension (speed) is constant. |
| Tension | Higher tension makes the pulse travel faster. |
| Reflection | A fixed end reflects the pulse upside down; a loose end reflects it right side up. |
| Damping | The wave loses energy and its amplitude decreases, like a guitar string fading. |
Common misconceptions
- “Bigger waves move faster.” In this simulation, amplitude does not change wave speed; tension does.
- “The string moves along with the wave.” Each piece of string moves up and down; the energy moves along.
- “Frequency and wavelength are unrelated.” At constant speed, they are inversely related.
Extensions
- Create a standing wave with a fixed end and find the frequencies that produce one, two and three loops.
- Connect to sound and musical instruments.
- Compare with energy transfer in our Energy Skate Park lab.
Frequently asked questions
Is the PhET Wave on a String simulation free?
Yes. PhET simulations from the University of Colorado Boulder are free to use online and work in most browsers.
What grade level is Wave on a String for?
It works well for grades 8–12, from introductory wave vocabulary to the wave equation in physics.
How do you measure wavelength in Wave on a String?
Pause the simulation, turn on the ruler and measure the distance between two neighboring crests.
Wave on a String makes invisible ideas visible. Pair it with our other simulation labs, such as the PhET circuit lab and Gravity and Orbits lab.
