10 free IB Physics C Wave Behaviour questions written in the style of IB Physics papers: 5 multiple-choice and 5 structured, each with its answer and mark scheme. 4 of them are A* challenge questions, built to catch the mistakes strong students still make.
This topic covers C.1 Simple harmonic motion, C.2 Wave model, C.3 Wave phenomena, C.4 Standing waves & resonance, C.5 Doppler effect. Work through the questions below, then generate a full C Wave Behaviour paper with a fresh set every time.
Generate a full C Wave Behaviour paper →A string of length 1.2 m is fixed at both ends. A standing wave with 2 antinodes forms when the string vibrates at 150 Hz.
What is the speed of waves on the string?
Answer: B
Monochromatic light of wavelength 500 nm is incident normally on a diffraction grating with 300 lines per mm.
What is the highest order of maximum that can be observed?
Answer: B
Which statements about electromagnetic waves in a vacuum are correct?
I. Their speed depends on their frequency.
II. They consist of oscillating electric and magnetic fields.
III. They are transverse waves.
Answer: C
An object performs simple harmonic motion. What is the phase difference between its displacement and its velocity, and between its displacement and its acceleration?
| displacement and velocity | displacement and acceleration | |
|---|---|---|
| A | π/2 | 0 |
| B | 0 | π |
| C | π | π/2 |
| D | π/2 | π |
Answer: D
A sound wave of frequency 500 Hz passes from air, where its speed is 340 m s−1, into water, where its speed is 1500 m s−1.
What is its wavelength in water?
Answer: D
A transverse wave of frequency 4.0 Hz and wavelength 1.5 m travels along a rope. Points P and Q on the rope are 0.50 m apart.
Calculate the speed of the wave.
Calculate the phase difference between P and Q.
The tension in the rope is increased by a factor of four. The wave speed is proportional to the square root of the tension. Calculate the new wavelength if the frequency is unchanged.
Distinguish between a transverse and a longitudinal wave.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | 6.0 m s−1 v = fλ = 6.0 m s−1 ✓ | 1 |
| (b) | 2π/3 rad 0.50/1.5 of a wavelength ✓ = 2π/3 rad (120°) ✓ | 2 |
| (c) | 3.0 m speed doubles to 12 m s−1 ✓ λ = 12/4.0 = 3.0 m ✓ | 2 |
| (d) | oscillation direction transverse: oscillations perpendicular to energy transfer ✓ longitudinal: oscillations parallel to energy transfer ✓ | 2 |
A guitar string of length 0.75 m is fixed at both ends. Its fundamental frequency is 147 Hz.
Calculate the speed of waves on the string.
State the frequency of the third harmonic and the number of nodes on the string in this mode.
A pipe closed at one end resonates in its fundamental mode at 147 Hz. Calculate the length of the pipe. (speed of sound = 340 m s−1)
Explain how a standing wave forms on the string.
State one difference between a standing wave and a travelling wave.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | 221 m s−1 λ = 2L = 1.50 m ✓ v = fλ = 221 m s−1 ✓ | 2 |
| (b) | 441 Hz; 4 nodes 441 Hz ✓ 4 nodes (including the ends) ✓ | 2 |
| (c) | 0.578 m L = λ/4 ✓ = 0.578 m ✓ | 2 |
| (d) | superposition of reflected waves waves reflect at the fixed ends ✓ two waves of equal frequency and amplitude travelling in opposite directions superpose ✓ | 2 |
| (e) | no energy transfer / amplitude varies a standing wave does not transfer energy / its amplitude varies with position ✓ | 1 |
A particle of mass 0.2 kg oscillates in simple harmonic motion with frequency 2.5 Hz and amplitude 4 cm. At t = 0 it is at maximum positive displacement.
Write down an equation for the displacement x as a function of time.
Calculate the total energy of the oscillation.
Calculate the kinetic energy when the displacement is half the amplitude.
Determine the first time at which the kinetic energy equals the potential energy.
Sketch graphs of kinetic energy and potential energy against time for one period of the motion.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | x = 0.04cos(15.7t) x = 0.04 cos(15.7t) m ✓ | 1 |
| (b) | 0.0395 J E = ½mω2A2 ✓ 0.0395 J ✓ | 2 |
| (c) | 0.0296 J Ek = ½mω2(A2 − x2) ✓ 0.0296 J (three quarters of the total) ✓ | 2 |
| (d) | 0.0500 s Ek = Ep when x = A√2 ✓ cos ωt = 1√2, ωt = π4 ✓ t = 0.0500 s ✓ | 3 |
| (e) | sin² and cos² shapes both oscillate at twice the frequency of the motion ✓ Ep starts at maximum, Ek at zero; their sum is constant ✓ | 2 |
A hydrogen line of wavelength 656.3 nm in the laboratory is observed at 662.9 nm in the light from a distant galaxy.
Calculate the speed of the galaxy relative to the Earth.
State whether the galaxy is moving towards or away from the Earth.
State why this equation is valid only for speeds much less than c.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | 3.0 × 106 m s−1 v = cΔλ/λ ✓ = 3.0 × 106 m s−1 ✓ | 2 |
| (b) | away away (red-shift) ✓ | 1 |
| (c) | non-relativistic it is the non-relativistic approximation of the Doppler shift ✓ | 1 |
A simple pendulum has length 0.80 m.
Calculate its period on Earth.
State the condition needed for the motion to be simple harmonic.
Calculate the period of the same pendulum on the Moon, where g = 1.6 m s−2.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | 1.8 s T = 2π√(L/g) ✓ = 1.8 s ✓ | 2 |
| (b) | small amplitude small angular amplitude (less than about 10°) ✓ | 1 |
| (c) | 4.4 s T = 2π√(0.80/1.6) ✓ = 4.4 s ✓ | 2 |
In the SL & HL syllabus, C Wave Behaviour covers C.1 Simple harmonic motion, C.2 Wave model, C.3 Wave phenomena, C.4 Standing waves & resonance, C.5 Doppler effect.
This page has 10 C Wave Behaviour questions with answers. For more, the free generator on mentorriyaz.in builds a new C Wave Behaviour paper with a full mark scheme each time you click.
Riyaz Shaikh has mentored IGCSE, IB and A Level students for 15+ years, one-on-one, online and in Mumbai. The hardest questions on this site are the ones he uses to find a student's weak points.
Meet Riyaz →Original IB-style practice questions written for mentorriyaz.in. These are not IB past paper questions, and this site is not affiliated with or endorsed by the International Baccalaureate Organization. Updated 2026-11-04. Paper generator · mentorriyaz.in