IGCSE Physics 0625 · Topic 3.1

IGCSE Physics General Properties of Waves Questions and Worked Solutions

50 topic-wise practice questions on General Properties of Waves (Unit 3: Waves), written to the Cambridge IGCSE Physics 0625 syllabus for 2026–2028, each with a step-by-step worked solution.

50 questions32 Core8 Extended10 Challenge116 marksTextbook §3.1 · pp. 128–135

Questions tagged Core are for all candidates (Papers 1 & 3). Questions tagged Extended are Supplement content (Papers 2 & 4). Questions 41–50 are harder Challenge questions. Try each question first, then tap Show solution to check your working.

Topic guide: General Properties of Waves

Waves transfer energy without transferring matter. Every wave has a wavelength, frequency, amplitude and speed. Waves are either transverse or longitudinal, and all waves can be reflected, refracted and diffracted.

Key formulas

v = f λ	wave speed v (m/s), frequency f (Hz), wavelength λ (m)	Core
f = 1 ÷ T	frequency and period T (s)	Core
f = number of waves ÷ time	from counting oscillations	Core

Prerequisite knowledge

Speed = distance ÷ time (1.2)
Standard form for large/small numbers

Exam tips & common mistakes

Amplitude is measured from the rest position, not crest to trough
Wavelength does not change during diffraction
If speed falls and frequency stays the same, wavelength must fall

Key facts from the syllabus (3.1)

Wavefront, wavelength, frequency, crest (peak), trough, amplitude and wave speed must be defined and identified on diagrams
Transverse: vibrations at right angles to the direction of travel (electromagnetic waves, water waves, seismic S-waves)
Longitudinal: vibrations parallel to the direction of travel (sound, seismic P-waves)
Reflection at a plane surface; refraction due to a change of speed; diffraction through a gap and at an edge
Ripple tank: shallow region (glass plate) shows refraction — waves slow down and wavelength decreases
Frequency does not change when a wave changes medium
Extended diffraction is greatest when the gap is about the same size as the wavelength; longer wavelengths diffract more at an edge

Textbook: §3.1 General properties of waves, pp. 128–135

Core[1 mark]

State what waves transfer from one place to another.

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Method: Waves carry energy, not matter.

Energy (without transferring matter)

Core[1 mark]

Define the wavelength of a wave.

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Method: Distance between matching points.

The distance between two neighbouring crests (or any two corresponding points)

Core[1 mark]

Define the amplitude of a wave.

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Method: Maximum displacement from rest.

The maximum displacement of a particle from its rest (undisturbed) position

Core[1 mark]

Define the frequency of a wave.

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Method: Waves per second.

The number of complete waves passing a point per second

Core[2 marks]

A wave has frequency 50 Hz and wavelength 0.40 m. Calculate its speed.

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Method: v = fλ.

v = 50 × 0.40 = 20.0 m/s

Core[2 marks]

A sound wave travels at 340 m/s with frequency 850 Hz. Calculate its wavelength.

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Method: λ = v ÷ f.

λ = 340 ÷ 850 = 0.400 m

Core[2 marks]

A water wave has speed 0.30 m/s and wavelength 0.015 m. Calculate its frequency.

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Method: f = v ÷ λ.

f = 0.30 ÷ 0.015 = 20.0 Hz

Core[3 marks]

A float bobs up and down 12 times in 20 s on water waves of wavelength 1.5 m. Calculate the frequency and the speed of the waves.

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Method: f = 12 ÷ 20, then v = fλ.

f = 0.600 Hz; v = 0.60 × 1.5 = 0.900 m/s

Core[2 marks]

State the direction of vibration in a transverse wave and give two examples.

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Method: Perpendicular to propagation.

At right angles to the direction of travel; e.g. light (electromagnetic waves), water waves, seismic S-waves

Core[2 marks]

State the direction of vibration in a longitudinal wave and give two examples.

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Method: Parallel to propagation.

Parallel to the direction of travel; e.g. sound, seismic P-waves

Core[1 mark]

State what happens to the speed of water waves when they pass into shallower water.

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Method: Speed decreases in shallow water.

The speed decreases

Core[2 marks]

Water waves pass from deep to shallow water. The frequency stays the same. State what happens to the wavelength and explain.

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Method: v = fλ with f constant.

The wavelength decreases, because the speed decreases and the frequency is unchanged

Core[1 mark]

Name the effect when waves spread out after passing through a narrow gap.

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Method: Diffraction.

Diffraction

Core[3 marks]

Describe how a ripple tank can be used to show refraction of water waves.

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Method: Glass plate creates shallow region.

Place a glass plate in the tank to make a shallow region; waves slow down there, so the wavefronts get closer together and change direction if they meet the boundary at an angle

Core[2 marks]

Describe how a ripple tank shows reflection at a plane surface.

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Method: Barrier.

Place a straight barrier in the tank; plane waves reflect so that the angle of incidence equals the angle of reflection

Core[2 marks]

State what is meant by a wavefront.

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Method: Line joining points in phase.

A line joining points on a wave that are in the same position (e.g. all along one crest)

Core[2 marks]

Describe how a slinky spring can show a transverse wave.

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Method: Move end side to side.

Move one end of the stretched spring repeatedly from side to side, at right angles to its length

Core[2 marks]

Describe how a slinky spring can show a longitudinal wave.

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Method: Push and pull end.

Push and pull one end repeatedly along the length of the spring

Core[1 mark]

Define a trough of a wave.

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Method: Lowest point.

The lowest point of a transverse wave

Core[2 marks]

A wave has wavelength 2.5 m and frequency 4.0 Hz. Calculate its speed.

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Method: v = fλ.

v = 10.0 m/s

Core[2 marks]

A radio wave travels at 3.0 × 10⁸ m/s with wavelength 1500 m. Calculate its frequency.

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Method: f = v/λ.

f = 2.0 × 10⁵ Hz

Core[2 marks]

Water waves travel at 0.50 m/s with frequency 2.5 Hz. Calculate the wavelength.

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Method: λ = v/f.

λ = 0.200 m

Core[3 marks]

A wave diagram shows 3 complete waves over a distance of 1.8 m. The frequency is 5.0 Hz. Calculate the wavelength and the speed.

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Method: λ = 1.8/3.

λ = 0.600 m; v = 3.00 m/s

Core[2 marks]

The vertical distance from crest to trough of a wave is 12 cm. State the amplitude.

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Method: Half crest-to-trough.

6.0 cm

Core[2 marks]

State what happens to the speed and wavelength of a wave if its frequency doubles in the same medium.

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Method: v constant.

Speed stays the same; wavelength halves

Core[2 marks]

State one example of a transverse wave and one of a longitudinal wave that occur in earthquakes.

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Method: S and P waves.

Transverse: seismic S-waves; longitudinal: seismic P-waves

Core[2 marks]

Describe what happens to plane water waves when they hit a straight barrier at an angle.

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Method: Reflection.

They are reflected, with the angle of reflection equal to the angle of incidence

Core[2 marks]

State which property of a wave stays the same when it passes from deep to shallow water.

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Method: Frequency.

The frequency

Core[3 marks]

Waves travel at 0.24 m/s in deep water with wavelength 1.2 cm and slow to 0.16 m/s in shallow water. Calculate the frequency and the wavelength in shallow water.

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Method: f from deep values.

f = 0.24 ÷ 0.012 = 20.0 Hz; λ = 0.16 ÷ 20 = 0.00800 m = 0.80 cm

Core[2 marks]

Explain why waves change direction when they enter shallow water at an angle.

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Method: Speed change.

One part of each wavefront slows down before the rest, so the wavefront turns

Core[2 marks]

Describe what happens to waves passing through a gap that is much wider than their wavelength.

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Method: Little diffraction.

They pass through mostly in a straight line with only slight spreading at the edges

Core[1 mark]

State what is transferred by a wave travelling along a rope.

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Method: Energy.

Energy (not the rope material)

Extended[2 marks]

Describe how the gap width affects diffraction of waves of a given wavelength.

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Method: Greatest when gap ≈ wavelength.

Diffraction is greatest when the gap is about the same size as the wavelength; a much wider gap gives little diffraction

Extended[2 marks]

Describe how wavelength affects diffraction at an edge.

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Method: Longer wavelength diffracts more.

Longer wavelengths diffract (bend round the edge) more

Extended[2 marks]

Explain why you can hear someone talking round a corner but cannot see them.

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Method: Sound wavelength ~ doorway size; light wavelength tiny.

Sound has wavelengths similar to the size of doorways so it diffracts a lot; light has a tiny wavelength so it diffracts very little

Extended[3 marks]

Waves of wavelength 2.0 cm pass through gaps of width 2.0 cm and 10 cm. Compare the diffraction.

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Method: Gap ≈ λ gives most spreading.

The 2.0 cm gap gives much more diffraction (wavefronts become nearly circular); the 10 cm gap gives little spreading, mainly at the edges

Extended[2 marks]

Explain why a long-wave radio signal can be received behind hills when a short-wave signal may not.

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Method: Diffraction.

Long wavelengths diffract more around the hills

Extended[2 marks]

Sound waves of wavelength 0.80 m and light of wavelength 5.0 × 10⁻⁷ m pass through a 0.90 m doorway. State which diffracts noticeably and explain.

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Method: Gap ≈ wavelength.

The sound, because its wavelength is similar to the doorway width; light's wavelength is far smaller

Extended[3 marks]

Sketch and describe the wavefronts after plane waves pass a gap equal to their wavelength.

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Method: Circular wavefronts.

The wavefronts emerge almost semicircular, spreading out widely, with the same wavelength

Extended[2 marks]

State whether the wavelength changes when waves are diffracted.

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Method: No.

No, the wavelength stays the same

Challenge questions

Harder, multi-step questions at the top end of the exam. Attempt these once you are confident with the questions above.

ChallengeCore[4 marks]

A wave machine produces 15 waves in 6.0 s. The distance between the first and sixth crest is 1.5 m. Calculate the frequency, wavelength and speed.

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Method: 5 wavelengths between crest 1 and crest 6.

f = 2.50 Hz; λ = 1.5 ÷ 5 = 0.300 m; v = 0.750 m/s

ChallengeCore[4 marks]

Water waves of frequency 4.0 Hz travel at 0.36 m/s in deep water and 0.24 m/s in shallow water. Calculate the wavelength in each region and explain which quantity stays the same.

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Method: λ = v/f.

Deep: 0.0900 m; shallow: 0.0600 m; frequency is unchanged (set by the source)

ChallengeCore[4 marks]

Describe and explain what happens to plane water waves that cross a straight boundary into shallow water at an angle of 40° to the boundary.

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Method: Refraction.

They slow down, wavelength decreases and the wavefronts bend so they travel more nearly perpendicular to the boundary (towards the normal)

ChallengeCore[3 marks]

Explain why a cork floating on water bobs up and down as waves pass but does not travel with them.

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Method: Energy not matter.

Waves transfer energy, not matter; the water particles (and cork) oscillate about a fixed position

ChallengeCore[4 marks]

A sound wave in air has frequency 680 Hz and travels at 340 m/s. It enters water where its speed is 1500 m/s. Calculate the wavelength in air and in water.

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Method: λ = v/f.

Air: 0.500 m; water: 2.21 m

ChallengeCore[4 marks]

Earthquake P-waves travel at 8.0 km/s and S-waves at 4.5 km/s. A station detects the S-wave 70 s after the P-wave. Calculate the distance to the earthquake.

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Method: d/4.5 − d/8.0 = 70.

d = 70 ÷ (1/4.5 − 1/8.0) = 720 km

ChallengeExtended[4 marks]

Waves of wavelength 1.0 cm in a ripple tank pass through gaps of 0.8 cm and 5.0 cm. Draw and describe the wavefronts after each gap.

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Method: Gap vs wavelength.

0.8 cm gap: strong diffraction, nearly circular wavefronts; 5.0 cm gap: wavefronts mostly straight with slight curving at the edges

ChallengeExtended[4 marks]

Explain why ships' foghorns use very low-frequency sound.

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Method: Long wavelength diffracts.

Low frequency means long wavelength, which diffracts around obstacles and spreads widely, so it is heard over a wider area

ChallengeExtended[3 marks]

Explain why you can hear a radio inside a building in a valley but may lose a TV signal using much shorter wavelengths.

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Method: Diffraction around hills.

Longer radio waves diffract around hills and buildings much more than short-wavelength signals

ChallengeExtended[4 marks]

Explain what happens to the amount of diffraction if (a) the wavelength is increased with a fixed gap, (b) the gap is made wider with a fixed wavelength.

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Method: Gap ≈ λ for most diffraction.

(a) Diffraction increases (b) Diffraction decreases

All IGCSE Physics topics ← 2.3.4 Consequences of Thermal Energy Transfer 3.2.1 Reflection of Light →

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