AQA GCSE Physics Foundation (8463), Foundation tier · Waves › Waves in air, fluids and solids
Practise Transverse and longitudinal waves. 7 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Waves transfer energy from one place to another without transferring matter. You need to describe the difference between transverse and longitudinal waves, give examples of each, and describe evidence that it is the wave, not the water or the air, that travels. Expect 1 to 3 mark recall and 'describe' questions.
Key facts
Waves transfer energy, not matter
Transverse: oscillations perpendicular to the direction of energy transfer
Longitudinal: oscillations parallel to the direction of energy transfer
Transverse examples: ripples on water, waves on a string, all electromagnetic waves
Longitudinal example: sound waves in air
Compression = particles close together; rarefaction = particles spread out
Sound needs a medium; it cannot travel through a vacuum
Notes
What a wave does
A wave is a repeated oscillation (vibration) that transfers energy from one place to another.
Waves transfer energy, and can carry information, but they do not transfer matter. The particles of the medium oscillate about fixed positions; only the wave moves on.
Sound waves and water waves need a medium (a substance) to travel through. Electromagnetic waves, such as light, can also travel through a vacuum.
Transverse waves
diagram
In a transverse wave the oscillations are perpendicular (at right angles) to the direction of energy transfer.
Transverse: the oscillation (blue) is at right angles to the energy transfer (red).
Examples: ripples on the surface of water, waves on a stretched string or rope, and all electromagnetic waves (light, radio waves, X-rays and so on).
A transverse wave has crests (peaks) and troughs.
Longitudinal waves
diagram
In a longitudinal wave the oscillations are parallel to the direction of energy transfer.
Example: sound waves in air. You can model one by pushing and pulling the end of a stretched slinky spring along its length.
A longitudinal wave has compressions (particles close together) and rarefactions (particles spread out).
Longitudinal: the particles oscillate back and forth along the direction of energy transfer.
In a sound wave, each air particle vibrates backwards and forwards about a fixed position and passes energy on to the next particle.
Evidence that the wave travels, not the medium
Ripples: a cork or a leaf floating on water bobs up and down as the ripples pass, but it does not travel across the water with them.
Sound: a loudspeaker playing music does not produce a wind, so the air is not flowing away from it. A strip of tissue paper held in front of a loudspeaker playing a low note vibrates backwards and forwards but is not blown away.
In both cases the energy moves on, but the water or air particles stay in about the same place.
How to answer each type of question
Recall: name or identify the type of wave
1 mark eachGrade 3
Transverse = oscillations at right angles to the direction of travel; longitudinal = oscillations along the direction of travel.
Remember: sound is longitudinal, and every electromagnetic wave is transverse.
Example. (a) Give one example of a longitudinal wave. (b) Which of these is a transverse wave? Tick (✓) one box. a sound wave in water / light from the Sun / a sound wave in air
Show the model answerHide the model answer
(a) Sound waves in air (1) (b) Light from the Sun (1)
Describe the difference between transverse and longitudinal waves
2 marksGrade 5
Write one statement about each type of wave.
Compare the direction of the oscillations with the direction of energy transfer.
Use the words 'perpendicular' and 'parallel'.
Example. Describe the difference between a transverse wave and a longitudinal wave.
Show the model answerHide the model answer
In a transverse wave the oscillations are perpendicular to the direction of energy transfer (1). In a longitudinal wave the oscillations are parallel to the direction of energy transfer (1).
Don’t lose marks
Saying the oscillations are parallel or perpendicular 'to the wave' without saying 'to the direction of energy transfer' (or 'to the direction the wave travels').
Saying that the water or air moves along with the wave. Waves transfer energy, not matter.
Giving sound as an example of a transverse wave, or light as a longitudinal wave.
Describing only one type of wave when the question asks for the difference.
More tips
Memory tricks
Longitudinal: think 'along'. The vibrations go along the direction of travel.
Transverse: think 'across'. A stadium wave is transverse: people move up and down while the wave moves sideways round the stadium.
Slinky test: push and pull along the spring = longitudinal; shake it side to side = transverse.
If it is electromagnetic, it is transverse. Sound is longitudinal.
Exam technique
For 'describe the difference', write a full sentence about each type of wave. A sentence about only one type can score one mark at most.
Use the specification words: oscillation, perpendicular, parallel, direction of energy transfer.
On a diagram of a longitudinal wave, label a compression where the lines or particles are closest together and a rarefaction where they are furthest apart.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
Give examples of transverse and longitudinal wavesTransverse: ripples on water and all electromagnetic waves, such as light. Longitudinal: sound waves in air.
Grade 4
State what waves transferWaves transfer energy (and can carry information) from place to place, but they do not transfer matter.
Grade 5
Describe how transverse and longitudinal waves differCompare the direction of the oscillations with the direction of energy transfer: perpendicular for transverse, parallel for longitudinal.
Grade 5
Identify compressions and rarefactionsIn a longitudinal wave, compressions are where the particles are close together and rarefactions are where they are spread out.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
The student then moves the end of the spring from side to side, at right angles to the length of the spring. This produces a transverse wave. Give one other example of a transverse wave.
Ripples on the surface of water (or any electromagnetic wave).
Maya drops a small cork into a still pond. Maya then throws a stone into the pond 3 m away from the cork. Ripples spread out across the surface of the water and pass the cork. Describe the motion of the cork as the ripples pass it.
The cork bobs up and down but stays in the same place.
Sound travelling through air is a longitudinal wave. State the direction of the oscillations of the air particles, relative to the direction the sound wave travels.
Parallel to the direction of travel.
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy6 marks
A student uses a long spring stretched along a bench to model two types of wave.
(a) The student moves one end of the spring backwards and forwards along the length of the spring. What type of wave does this produce? Tick (✓) one box.[1]
Electromagnetic
Longitudinal
Transverse
(b) The student then moves the end of the spring from side to side, at right angles to the length of the spring. This produces a transverse wave. Give one other example of a transverse wave.[1]
(c) Describe the difference between a longitudinal wave and a transverse wave.[2]
(d) In a longitudinal wave on the spring, there are regions where the coils are closer together than normal and regions where the coils are further apart than normal. Name these two types of region.[2]
Show the answer and mark scheme
(a)Answer: Longitudinal
(b)Answer: Ripples on the surface of water (or any electromagnetic wave).
ripples on the surface of water / any electromagnetic wave, e.g. light / waves on a string / S-waves
(c)Answer: In a longitudinal wave the oscillations are parallel to the direction of energy transfer; in a transverse wave they are perpendicular to it.
longitudinal: the oscillations are parallel to the direction of energy transfer
transverse: the oscillations are perpendicular to the direction of energy transfer
(d)Answer: Closer together: compression. Further apart: rarefaction.
(coils closer together:) compression(s)
(coils further apart:) rarefaction(s)
Question 2Medium6 marks
Maya drops a small cork into a still pond. Maya then throws a stone into the pond 3 m away from the cork. Ripples spread out across the surface of the water and pass the cork.
(a) Describe the motion of the cork as the ripples pass it.[1]
(b) Explain how the motion of the cork shows that it is the wave, and not the water, that travels across the pond.[2]
(c) A candle flame is placed a few centimetres in front of a loudspeaker. When the loudspeaker plays a loud, low-pitched note, the flame moves backwards and forwards but it is not blown away from the loudspeaker. Explain what this shows about the sound wave travelling through the air.[3]
Show the answer and mark scheme
(a)Answer: The cork bobs up and down but stays in the same place.
it moves up and down (in the same place) / it is not carried along with the ripples
(b)Answer: The cork, and the water it floats on, only oscillates about a fixed point, so the water does not move across the pond; only the wave (energy) does.
the cork (and the water around it) only oscillates about a fixed position
so the water is not carried across the pond; the wave transfers energy without transferring the water
(c)Answer: The air oscillates backwards and forwards along the direction the sound travels (a longitudinal wave), but the air is not carried away from the loudspeaker; only the wave travels.
the air (particles) oscillate / vibrate backwards and forwards
parallel to the direction of energy transfer / sound is a longitudinal wave
the air itself does not travel away from the loudspeaker; only the wave (energy) travels through the air