Suggested practical

Measure the speed, frequency and wavelength of waves in a ripple tank

Jonny Nelson explains waves in a fluid with a GCSE Physics practical experiment

A ripple tank can be used to measure and calculate frequency, wavelength and the speed of waves on the water's surface. A ripple tank is a transparent shallow tray of water with a light shining down through it onto a white card below. The light allows you to see the motion of the ripples created on the water's surface more easily. Ripples can be made by hand but to generate regular ripples it is better to use a motor.

A ripple tank, on a table, with surrounding equipment including a lamp, power supply, motor and wooden rod.

Aim of the experiment

To measure the frequency, wavelength and speed of waves in a ripple tank.

Method

  1. Set up the ripple tank as shown in the diagram with about 5 cm depth of water.
  2. Adjust the height of the wooden rod so that it just touches the surface of the water.
  3. Switch on the lamp and motor and adjust the speed of the motor until low frequency waves can be clearly observed.
  4. Measure the length of a number of waves then divide by the number of waves to calculate the wavelength. It may be more practical to take a photograph of the card with the ruler and take your measurements from the still picture.
  5. Count the number of waves passing a point in ten seconds then divide by ten to record frequency.
  6. Calculate the speed of the waves using: wave speed = frequency × wavelength.

Example results table

In this example 12 waves have been measured.

Length of 12 waves (cm)Wavelength (cm)Number of waves in 10 secondsFrequency (Hz)Wave speed (cm/s)
...............

Risks/hazards

HazardConsequenceControl measures
Electrical components near waterShock and/or damage to componentsSecure electrical components before adding water, taking care not to splash