A standing wave is a stable pattern of oscillation that does not appear to travel across a wave medium.

Tension is the name for the force applied to a stretched string or rope. Without any tension a string or rope would be slack.

Division is the mathematical inverse (opposite) of multiplication, so the inverse of ×2 is ÷2 (which can also be written as ×½).

A proportion is an exact mathematical comparison, such as double,  half (50%), triple, a third, quadruple, a quarter etc.

Control variables are the quantities that must be kept the same during experiments so they don’t affect results.

Measuring waves on a string

Physics

In the Electromagnetic waves unit, they will build on this knowledge to learn about the reflection and refraction of light, other types of electromagnetic radiation in the EM spectrum and the helpful and harmful effects of each type of radiation.

In the Waves unit, pupils learnt about the properties and propagation of transverse and longitudinal waves.

This unit covers wave motion, including amplitude, wavelength, frequency, and velocity. It explains transverse and longitudinal waves, reflection, and absorption. The focus is on measuring wave speed, and sound interactions, applying formulas, and conducting accurate experiments.

Measuring waves

Physical activity and equipment requiring safe use

In an experiment, a variable that must be kept the same so it does not affect the results, is called a {{}} variable.

Which images show a standing wave on a string?

The length of string oscillating in this image is 90 cm. What is the wavelength of the waves?

Measure the length of the string using a metre rule.

Slowly increase the frequency of the oscillator until a standing wave is seen.

Record the frequency from the signal generator and work out the wavelength.

Calculate the wave speed using speed = frequency x wavelength.

Starting with the measurement of the string length, put the steps in order to find the speed of waves on a string from a standing wave pattern.

Suggest which of the following could affect the speed of waves on a string? 

The wavelength would reduce from 20 cm to 5 cm

The wavelength would reduce from 20 cm to 10 cm

The wavelength would increase from 20cm to 40 cm

The wavelength would increase from 20 cm to 80 cm

Waves on a string have a frequency of 10 Hz and a wavelength of 20 cm. The frequency is increased from 10 Hz to 40 Hz. Nothing else changed. How would the wavelength be affected?

Some waves on a string have a frequency of 3 Hz and a wavelength of 12 cm. How would you calculate the wave speed in m/s?

what you change in each test to see what effect it has

what you monitor to see if it changes in response

what you keep the same so they don't affect the results

In experiments, what are the different types of variables?

the middle point of a wave, halfway along a wavelength

When a wave travels along a string, what is the wave medium?

increasing the frequency also increases the wavelength

increasing the frequency decreases the wavelength

increasing the frequency does not affect the wavelength

If waves of different frequencies and wavelengths all have the same speed, what happens if you increase the frequency of waves?

Content guidance

Risk assessment required - equipment

Adult supervision required

This lesson will be removed by end of Summer Term 2025.

Measuring waves on a string

Lesson outcome

Content guidance

This lesson will be removed by end of Summer Term 2025.