Water waves in a ripple tank have a wavelength of 0.02 m and a frequency of 15 Hz. Calculate the wave speed.
[2 marks]
Total for this question: 2
Physics required practicals
Waves in a ripple tank and a solid
AQA 4.6 · RP8
GCSE Physics (8463) · Required practical 8 — method, variables, the marks examiners report students losing.
Board and spec code confirmed against AQA 8463 · registry checked 2026-07-17How this checking works
Measure the frequency, wavelength and speed of waves in a ripple tank (water waves) and in a stretched string, using wave speed = frequency x wavelength.
Apparatus
- Ripple tank with a lamp above, a motor and dipper, and a power supply
- White screen or paper below the tank, and a ruler
- Stroboscope (or a phone camera) to freeze the wave pattern
- For the string: signal generator, vibration generator, string, pulley and masses
Method
- 1Ripple tank: switch on the dipper to make waves and shine the lamp through so wavefronts show on the screen below.
- 2Measure the wavelength by measuring the distance across several wavefronts and dividing; read the frequency from the motor setting (or use a strobe to freeze the pattern).
- 3Calculate wave speed = frequency x wavelength.
- 4Waves in a solid: attach the string to a vibration generator, run it over a pulley with masses, and adjust the signal generator until a clear standing wave forms.
- 5The wavelength is twice the distance between adjacent nodes; take the frequency from the generator and again use wave speed = frequency x wavelength.
Results & processing
- Wave speed = frequency x wavelength (v = f x wavelength).
- Measure across several wavelengths and divide to reduce the percentage error; on a string, wavelength = 2 x the distance between adjacent nodes.
Where students lose marks
Measuring only one wavelength.
Fix: Measure across several wavelengths and divide by the number, which reduces the percentage (measurement) error.
Confusing the frequency of the source with the wavelength.
Fix: Frequency comes from the motor or signal generator; wavelength is a distance you measure on the pattern.
On a string, taking node-to-node distance as the whole wavelength.
Fix: The distance between adjacent nodes is half a wavelength, so wavelength = 2 x that distance.
Improve the method
- Measure across as many wavelengths as possible, then divide.
- Use a stroboscope to freeze the ripple pattern so it can be measured.
- Repeat measurements and take a mean; use a shadow/screen so the wavefronts are clear.
Try it — exam-style
Easy
ORIGINAL
Medium
ORIGINAL
A student measures the distance across 10 wavelengths as 0.60 m. State the wavelength, and explain why measuring across 10 wavelengths is better than measuring one.
[2 marks]
Total for this question: 2
Questions are written in the style of past AQA papers — never copied from them.
Drill it properly
Stuck on waves in a ripple tank and a solid?
Wave-measurement questions reward the many-wavelengths trick and the node-to-node rule — I drill both. Free intro call, then a free first lesson.