General properties of waves and sound

Wave motion and quantities, transverse and longitudinal waves, sound, loudness, pitch and echoes.

SEC G3 Combined Science Physics component 2027
6 lessons

Before you begin

Ripples on a pond, a vibrating spring and the sound of a voice are all waves: they carry energy from place to place without carrying the material with them. The lessons start by describing wave motion on ropes, springs and water and sorting waves into transverse and longitudinal. They then measure a wave by its amplitude, wavelength, period and frequency and use v = fλ. They finish with sound: how it is made and carried, what decides its loudness and pitch, and how echoes measure distance.

Be comfortable with: SI prefixes, because wave calculations use ms, kHz and cm, and reading graphs.

Learning goals

Describe wave generation by vibrating sources, ropes and springs
Describe ripple-tank waves using wavefronts
Explain that waves transfer energy
Explain that wave energy transfer does not transfer matter
Compare transverse and longitudinal waves and give examples
Use amplitude, frequency and wavelength to describe wave motion
Define and use wave speed and period and interpret wave graphs
Recall and apply wave speed = frequency × wavelength
Explain sound production by vibration and the need for a medium
Describe sound using compressions and rarefactions
Relate sound loudness to amplitude and pitch to frequency
Explain reflected-sound echoes and use them to measure distance

Syllabus statements covered

describe what is meant by wave motion as illustrated by vibrations in ropes and springs and by waves in a ripple tank (including use of the term wavefront)
show an understanding that waves transfer energy without transferring matter
define and use the terms speed, frequency, wavelength, period and amplitude including graphical representations
recall and apply the relationship speed of wave = frequency × wavelength to new situations or to solve related problems
compare transverse and longitudinal waves and give suitable examples of each
show an understanding that sound can be produced by vibrating sources and a medium is required for the transmission of sound.
describe the longitudinal nature of sound waves in terms of the processes of compression and rarefaction
relate loudness of a sound wave to its amplitude and pitch to its frequency
describe how the reflection of sound may produce an echo, and how this may be used for measuring distances

Lessons

Work through them in order.

Practise and check

Or choose

Topic reference

Quick reference

Idea	Relationship or meaning	Note
amplitude	the maximum displacement from the rest position	larger amplitude: louder sound
wavelength, λ	the distance between neighbouring crests, or between neighbouring compressions	unit m
period, T	the time for one complete wave	T = 1/f
frequency, f	the number of complete waves per second	unit Hz; higher frequency: higher pitch
wave speed	v = fλ	use metres, seconds and hertz
echo	2d = vt	t covers the journey there and back

Core knowledge to remember

Waves transfer energy without transferring matter.
In a transverse wave the vibrations are at right angles to the direction the wave travels; in a longitudinal wave they are along it.
Speed of wave = frequency × wavelength.
Sound is produced by vibrating sources, and a medium is needed to transmit it.
Sound is a longitudinal wave made of compressions and rarefactions.
The loudness of a sound depends on its amplitude; its pitch depends on its frequency.
An echo is a reflected sound, and timing it can be used to measure distances.

Common mistakes

Saying a wave carries the material of the medium along with it.
Measuring amplitude from crest to trough instead of from the rest position.
Forgetting to change ms to s or kHz to Hz before using v = fλ or T = 1/f.
Saying sound can travel through a vacuum.
Saying a taller trace on a graph means a higher pitch.
Forgetting to halve the distance travelled by an echo.