A Level Physics 7.2 Transverse and Longitudinal Waves MCQs – 30 Practice Questions with Answers (Cambridge 9702)

Free practice questions for Cambridge International AS & A Level Physics (9702), Section 7.2 Transverse and Longitudinal Waves. Work through all 30 original MCQs, then open the Show Answer toggles to check your answers with full explanations.

Formula recap: v = fλ  |  T = 1 / f  |  In a transverse wave the oscillations are perpendicular to the direction of energy transfer; in a longitudinal wave they are parallel to it. See the full A Level Physics Formula Sheet for every equation you need.

Transverse Waves

Q1. A transverse wave is best defined as a wave in which the oscillations of the particles are

  • (A) parallel to the direction of energy transfer
  • (B) perpendicular to the direction of energy transfer
  • (C) in the same direction as the wave is travelling
  • (D) stationary while the energy moves forward
Show Answer

Answer: B – In a transverse wave the particles oscillate at right angles (perpendicular) to the direction in which the wave transfers energy.

Q2. Which of the following waves is transverse?

  • (A) Sound waves in air
  • (B) Ultrasound waves in water
  • (C) Light waves in a vacuum
  • (D) Pressure waves from a loudspeaker
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Answer: C – Light and all other electromagnetic waves are transverse: the electric and magnetic fields oscillate perpendicular to the direction of travel. Sound and ultrasound are longitudinal.

Q3. On a transverse wave travelling along a rope, a crest is

  • (A) a point of maximum displacement in one direction
  • (B) a region where the particles are closest together
  • (C) a point where the displacement is always zero
  • (D) a region where the pressure is highest
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Answer: A – A crest is the highest point of the wave, where displacement from the equilibrium position is a maximum in one direction. The corresponding maximum in the opposite direction is a trough. Regions of particles close together are compressions, found in longitudinal waves.

Q4. A ribbon is tied to a long rope. One end of the rope is moved up and down to send transverse waves along it. What is observed about the motion of the ribbon?

  • (A) It travels along the rope with the wave
  • (B) It moves in a circle around the rope
  • (C) It gradually drifts towards the far end of the rope
  • (D) It moves up and down about a fixed position and is not carried along
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Answer: D – The ribbon only oscillates up and down about its equilibrium position. The wave transfers energy along the rope, but the particles of the rope (and the ribbon) are not transported with the wave.

Q5. A displacement-distance graph is drawn for a transverse wave on a rope at one instant. The wavelength of the wave can be read from the graph as the distance between

  • (A) a crest and the next trough
  • (B) two adjacent crests
  • (C) the highest and lowest points of the graph
  • (D) the first and last points where the graph crosses zero
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Answer: B – The wavelength is the distance between two neighbouring points that are in phase, such as two adjacent crests or two adjacent troughs. A crest to the next trough is only half a wavelength.

Q6. A transverse wave travels along a stretched string with frequency 5.0 Hz and wavelength 0.40 m. What is the speed of the wave?

  • (A) 0.080 m/s
  • (B) 12.5 m/s
  • (C) 2.0 m/s
  • (D) 20 m/s
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Answer: C – v = fλ = 5.0 × 0.40 = 2.0 m/s.

Q7. Which phenomenon provides direct evidence that light waves are transverse?

  • (A) Polarisation
  • (B) Diffraction
  • (C) Refraction
  • (D) Reflection
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Answer: A – Only transverse waves can be polarised, because their oscillations have a direction perpendicular to the travel direction that can be selected by a filter. Diffraction, refraction and reflection are shown by all waves, transverse and longitudinal. Polarisation is covered fully in Section 7.5.

Q8. A small cork floats on water as a transverse surface wave passes. Which statement describes the motion of the cork?

  • (A) It moves steadily in the direction of the wave
  • (B) It moves in the opposite direction to the wave
  • (C) It bobs up and down about a fixed position
  • (D) It stays completely still because the wave is transverse
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Answer: C – The cork follows the oscillation of the water surface, rising to a crest and falling to a trough, but it is not carried along with the wave.

Q9. Which list contains only transverse waves?

  • (A) Sound, ultrasound, water waves
  • (B) Microwaves, light, waves on a stretched rope
  • (C) Light, sound, waves on a slinky spring pushed and pulled
  • (D) X-rays, ultrasound, seismic P waves
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Answer: B – Microwaves and light are electromagnetic waves, and rope waves are set up by sideways oscillations; all three are transverse. Sound, ultrasound and seismic P waves are longitudinal.

Q10. On a displacement-distance graph for a transverse wave, the amplitude is measured as

  • (A) the distance between two adjacent crests
  • (B) the total height from a trough to a crest
  • (C) the length of one complete wave cycle
  • (D) the maximum displacement from the equilibrium (zero) line to a crest
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Answer: D – Amplitude is the maximum displacement of a particle from its equilibrium position, so it is read from the zero line to the top of a crest (or to the bottom of a trough). Trough-to-crest height is twice the amplitude.

Longitudinal Waves

Q11. A longitudinal wave is best defined as a wave in which the oscillations of the particles are

  • (A) parallel to the direction of energy transfer
  • (B) perpendicular to the direction of energy transfer
  • (C) in circles around the direction of travel
  • (D) at 45 degrees to the direction of travel
Show Answer

Answer: A – In a longitudinal wave the particles vibrate back and forth along the same line as the wave travels, producing compressions and rarefactions.

Q12. In a longitudinal sound wave, a compression is a region where the air particles are

  • (A) furthest apart and the pressure is lowest
  • (B) stationary and the pressure is zero
  • (C) closest together and the pressure is highest
  • (D) moving fastest sideways
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Answer: C – A compression is where the particles have been pushed together, so the density and pressure there are a maximum. The opposite region, where particles are spread out and pressure is lowest, is a rarefaction.

Q13. For a longitudinal wave, one wavelength is equal to the distance between

  • (A) a compression and the nearest rarefaction
  • (B) two adjacent compressions
  • (C) the first and last compression produced
  • (D) a particle and its equilibrium position
Show Answer

Answer: B – Wavelength is the distance between two adjacent points in phase. For a longitudinal wave this is the spacing between neighbouring compressions (or neighbouring rarefactions). A compression to the next rarefaction is half a wavelength.

Q14. A loudspeaker cone vibrates in and out, sending sound through air. The sound wave formed is longitudinal because

  • (A) the air particles move up and down
  • (B) the air particles move in circles
  • (C) the wave can be polarised by the cone
  • (D) the air particles vibrate back and forth along the direction the sound travels
Show Answer

Answer: D – The cone pushes the air forward and pulls it back, so the air particles oscillate parallel to the direction of propagation, alternately forming compressions and rarefactions. Sound cannot be polarised.

Q15. At the centre of a compression in a sound wave, which statement is correct?

  • (A) The displacement of the air particles is a maximum and the pressure is a maximum
  • (B) The displacement is a maximum and the pressure is a minimum
  • (C) The displacement is zero and the pressure is a minimum
  • (D) The displacement of the air particles is zero and the pressure is a maximum
Show Answer

Answer: D – At the centre of a compression the particles are momentarily at their equilibrium displacement (zero displacement on a displacement-distance graph), even though they are bunched closest together there, giving maximum pressure. Displacements are a maximum between a compression and a rarefaction.

Q16. A longitudinal wave is demonstrated by pushing and pulling one end of a slinky spring along its length. A single coil of the slinky

  • (A) oscillates back and forth along the length of the spring
  • (B) oscillates up and down perpendicular to the spring
  • (C) travels with the wave to the far end
  • (D) rotates around the axis of the spring
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Answer: A – Each coil vibrates about its own equilibrium position, backwards and forwards parallel to the spring. It is the pattern of compressions and rarefactions that travels, not the coils themselves.

Q17. Sound waves cannot be polarised. The reason is that

  • (A) sound travels too slowly
  • (B) sound needs a material medium
  • (C) sound has too long a wavelength
  • (D) the oscillations are along the direction of travel, so there is no sideways oscillation to select
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Answer: D – Polarisation works by allowing oscillations in only one plane perpendicular to the travel direction. A longitudinal wave has no perpendicular oscillation at all – its particles move along the line of travel – so a polarising filter cannot select any part of it.

Q18. An ultrasound wave in water has frequency 2.0 × 106 Hz and speed 1500 m/s. What is its wavelength?

  • (A) 7.5 × 10-1 m
  • (B) 7.5 × 10-4 m
  • (C) 3.0 × 109 m
  • (D) 1.3 × 103 m
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Answer: B – λ = v / f = 1500 / (2.0 × 106) = 7.5 × 10-4 m (0.75 mm). Short wavelengths like this are why ultrasound can form detailed images.

Q19. A pressure-distance graph is drawn for a sound wave. Along one complete wavelength, the graph shows

  • (A) pressure constant throughout
  • (B) one pressure maximum only, at a rarefaction
  • (C) a pressure maximum at the compression and a pressure minimum at the rarefaction
  • (D) pressure maximum where the displacement is maximum
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Answer: C – Pressure rises above atmospheric at a compression and falls below atmospheric at a rarefaction, so one wavelength of the pressure graph contains one peak and one trough. Where pressure is at an extreme, displacement is zero.

Q20. A student claps and hears an echo from a wall. The sound reaching the wall and returning is a longitudinal wave because in the air

  • (A) the particles travel all the way to the wall and back
  • (B) the particles oscillate across the direction of travel
  • (C) the particles oscillate in line with the sound’s direction of travel, forming compressions and rarefactions
  • (D) the pressure stays constant along the path
Show Answer

Answer: C – All sound in air is longitudinal: each air particle vibrates about a fixed position along the direction the sound is travelling, passing the disturbance on as compressions and rarefactions.


Comparing & Identifying Wave Types

Q21. Seismic (earthquake) waves include P waves and S waves. Which row correctly identifies them?

  • (A) P waves: transverse; S waves: longitudinal
  • (B) P waves: longitudinal; S waves: transverse
  • (C) Both P and S waves are longitudinal
  • (D) Both P and S waves are transverse
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Answer: B – P (primary) waves are compression waves, so they are longitudinal, like sound. S (secondary) waves shake the ground sideways, so they are transverse.

Q22. Seismic S waves are never detected from earthquakes on the opposite side of the Earth. This is evidence that part of the Earth’s interior is liquid, because S waves

  • (A) cannot travel through liquids, whereas longitudinal P waves can
  • (B) travel faster in liquids than in solids
  • (C) are reflected by all solid rock
  • (D) are absorbed by the atmosphere
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Answer: A – Transverse waves need a material that can be sheared sideways, so they cannot pass through a liquid. S waves disappear where their path would cross the Earth’s liquid outer core, while longitudinal P waves continue through it (at changed speed and direction).

Q23. A transverse wave travels from left to right along a rope. At the instant shown in a diagram, a marked particle is exactly at a crest. In the next moment, the particle moves

  • (A) to the right, with the wave
  • (B) to the left, against the wave
  • (C) downward, back towards its equilibrium position
  • (D) upward, further from equilibrium
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Answer: C – A particle at a crest is at maximum displacement and momentarily at rest; it then accelerates back towards (and through) the equilibrium position. It never travels along the rope with the wave.

Q24. Which property is shown by both transverse and longitudinal waves?

  • (A) Polarisation
  • (B) Oscillations perpendicular to the direction of travel
  • (C) Compressions and rarefactions
  • (D) Diffraction at the edge of an obstacle
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Answer: D – All waves – transverse and longitudinal – can be reflected, refracted and diffracted, and all obey v = fλ. Polarisation is only possible for transverse waves, and compressions and rarefactions belong only to longitudinal waves.

Q25. Which row gives the correct classification of all three waves?

  • (A) Microwaves: longitudinal; Water waves: transverse; Sound: transverse
  • (B) Microwaves: transverse; Water waves: transverse; Sound: longitudinal
  • (C) Microwaves: transverse; Water waves: longitudinal; Sound: longitudinal
  • (D) Microwaves: longitudinal; Water waves: longitudinal; Sound: transverse
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Answer: B – Microwaves are electromagnetic waves, so they are transverse; water surface waves oscillate up and down, also transverse; sound in air travels as compressions and rarefactions, so it is longitudinal.

Q26. A water wave has speed 1.5 m/s and wavelength 0.30 m. What is the frequency of the wave, and what type of wave is it?

  • (A) 5.0 Hz, transverse
  • (B) 5.0 Hz, longitudinal
  • (C) 0.20 Hz, transverse
  • (D) 2.0 Hz, longitudinal
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Answer: A – f = v / λ = 1.5 / 0.30 = 5.0 Hz. Surface water waves displace the surface up and down, perpendicular to the travel direction, so they are transverse.

Q27. In an experiment, a wave is passed through two polarising filters in turn. Rotating the second filter changes the transmitted intensity to zero. The wave must be

  • (A) longitudinal, because only longitudinal waves can be blocked
  • (B) a sound wave, because sound is easily blocked
  • (C) transverse, because only transverse waves can be polarised
  • (D) either type, because all waves can be polarised
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Answer: C – Polarisation is the test for a transverse wave: the filters select oscillations in one perpendicular plane only. A longitudinal wave has no perpendicular oscillations, so it cannot show this effect.

Q28. Which statement is correct for both transverse and longitudinal waves?

  • (A) They can both be polarised
  • (B) Their particles both oscillate perpendicular to the energy flow
  • (C) They both produce compressions and rarefactions
  • (D) They both transfer energy without any net transfer of the particles of the medium
Show Answer

Answer: D – In both wave types the particles oscillate about fixed equilibrium positions; energy is transferred from place to place, but the medium itself is not carried along. The other statements each apply to only one wave type.

Q29. A longitudinal wave travels from left to right through a slinky. A marked coil is at the centre of a rarefaction. Which description of the coil is correct?

  • (A) It is displaced as far right as it can go
  • (B) Its displacement is zero, and the coils around it are at their most spread out
  • (C) Its displacement is a maximum to the left
  • (D) It moves steadily to the right with the wave
Show Answer

Answer: B – At the centre of a rarefaction (and of a compression) a particle is passing through its equilibrium position, so its displacement is zero. What is special about a rarefaction is the spacing: the coils there are furthest apart, giving minimum density and pressure.

Q30. A wave machine produces waves on the surface of a tank of water. When a straight barrier with a wide gap is placed in the tank, the waves spread out after the gap. A second experiment shows the same spreading for sound waves passing through a doorway. The spreading is diffraction, and it happens because

  • (A) all waves spread when they pass through a gap or past an edge, whatever their type
  • (B) only transverse waves can spread after a gap
  • (C) only longitudinal waves can spread after a gap
  • (D) diffraction proves both waves are electromagnetic
Show Answer

Answer: A – Diffraction – the spreading of waves through gaps and around edges – is a property of every wave, transverse or longitudinal, and is strongest when the gap width is similar to the wavelength. It is one of the shared wave behaviours, unlike polarisation.

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