Waves Required GCSE Physics Practical

Properties of waves in liquids and solids.

During this experiment, students are required to make observations to assess the suitability of different apparatus used to measure the frequency, wavelength and speed of waves in a ripple tank, and in a solid by observing waves on a length of string. A video showing the experimental set up for the waves on a string practical can be found over on our YouTube Channel.

Equipment (per pair of participants)

• Safety glasses
• Metre ruler
• Vibration generator
• Power signal generator
• Connecting leads
• String

• Hanging slotted mass sets
(100g, 1kg)
• Wooden bridge
• Bench pulley
• Retort stand
• Large sheet of white paper

Equipment for the class to share

• Ripple tank

Method

Activity 1: Observing Waves in a Liquid

Equipment: Ripple tank | Metre ruler | White paper

Instructions:

Setup:

Arrange several ripple tanks for the class to share, pre-assembled by technical staff.
Add 5mm of water to each tank.
Attach the rod-shaped dipper to the wave generator.
Place a sheet of white paper on the ripple tank’s projection surface (this could be either below the tank or on the screen at the front, depending on the tank model).

Start Experiment:

Switch on the ripple tank lamp and the wave generator.
Adjust the motor speed to produce clear, low-frequency waves in the water.
Adjust the lamp height to improve the visibility of the wave patterns on the viewing area.

Measuring Wavelength:

Hold a metre ruler at right angles to the waves.
Measure the distance across multiple waves to get a more accurate result, then take an average.
Divide this measurement by the number of waves measured to calculate the wavelength.
Record the wavelength in a table.

Measuring Frequency:

Count the number of waves passing a specific point over a set time (e.g., 10 seconds).
Divide the number of waves by the time period (e.g., 10 waves in 10 seconds = 1 Hz) to calculate the frequency.

Calculate Wave Speed:

Use the formula:
Wave Speed = Frequency x Wavelength

Activity 2: Observing Waves in a Solid

Instructions:

Setup:

Connect the vibration generator to the power signal generator (low impedance sockets).
Attach one end of a string to the armature of the vibration generator.
Extend the string over the wooden bridge and pulley, ensuring it remains tight by attaching a mass hanger with weights at the end.

Start Experiment:

Turn on the power signal generator and select Sine wave mode.
Set the frequency range on the generator to 10-110 Hz.
Adjust the frequency dial to produce as many half wavelengths as possible. For example, 90 Hz may produce 3 half wavelengths on a 1-meter string.
Adjust the amplitude for clear wavelength visibility.

Measuring Wavelength:

Measure the length across multiple half wavelengths.
Divide the total length of the string (from the vibration generator to the pulley) by the number of half waves.
Multiply by two to obtain the full wavelength.

Determining Frequency:

The frequency is displayed on the power signal generator.

Calculate Wave Speed:

Use the formula:
Wave Speed = Frequency x Wavelength

Technician tips

The wooden bridge required could be produced using excess wood from the Design Technology department.
The number of ripple tanks, vibration generators and power signal generators required could be reduced, depending on your science department budget.
The two activities could be done as a circus.
If a power signal generator is unavailable to drive the vibration generator, a bench signal generator could be used alongside a power amplifier. Feeding the signal from the bench signal generator through a power amplifier will boost the signal enough to drive the vibration generator.