Unit 4 · Waves and Superposition

What Cambridge International AS & A Level Physics (9702) Unit 4 covers

Use this map to connect each assessed skill to the relationship or representation that makes it visible.

Waves and Superposition

Connect the published share to the unit model

Multiplying 6.00 Hz by 0.240 m gives a propagation speed of 1.44 m/s. The separate 0.180 m path difference occupies 0.750 of a wavelength and therefore corresponds to 1.50π rad.

A position trace supplies wavelength from horizontal spacing, while a time trace supplies period. Reading the wrong kind of axis would feed the wrong quantity into v = fλ.

The 270° phase difference is neither a maximum nor a minimum in the stated example. That physical conclusion completes the numerical phase calculation.

Read the horizontal axis before choosing a relation: a position trace supplies wavelength, whereas a time trace supplies period. Select the propagation or superposition equation only after that identification. If path difference is involved, convert it to a fraction of a wavelength and then to phase, finally naming the resulting constructive, destructive or intermediate behavior.

The decision that organizes this unit

Define the system and choose the route before calculating

Multiply 6.00 Hz by 0.240 m

Mechanism route and repair branches

Relationships to preserve

• Wave speed: Frequency and wavelength describe propagation.
• Phase: Path difference is 0.750 wavelength.
• Interference: 270° is not 0° or 180°.

Representations to read

• A graph of displacement against position (m).
• A formula card that explains speed uses frequency with wavelength, while phase uses path difference relative to wavelength.
• A table linking key concept, why it matters, visible method.

Branches to reject

• Treating 0.180 m path difference as the wavelength
• Reporting 0.750 as radians rather than cycles
• Treating position as elapsed time

How Cambridge International AS & A Level Physics (9702) assesses Waves and Superposition

What a complete response must make visible

Match the task to evidence that a reader can audit, then check the most likely reasoning failure before finalizing the response.

Worked example: wave speed, phase and interference

Read each question as it appears on the exam paper, choose your answer, then tap it to see the feedback.

Practice 1: Wave speed and phase difference

Practice 2: Reading a wave trace

Key terms for Unit 4: Waves and Superposition

Models, uses, and boundaries

Waves and Superposition

Speed uses frequency with wavelength, while phase uses path difference relative to wavelength. Use this relationship when speed uses frequency with wavelength, while phase uses path difference relative to wavelength..

Worked example: wave speed, phase and interference

The calculation keeps meters in both Δx and λ so their ratio is dimensionless before multiplication by 2π. Use this relationship when the calculation keeps meters in both Δx and λ so their ratio is dimensionless before multiplication by 2π..

Waves and Superposition: change one condition

Coordinates on this sinusoid describe displacement at stated positions along the wave. Use this relationship when coordinates on this sinusoid describe displacement at stated positions along the wave..

Waves and Superposition: test proposed results

Proposed answers must distinguish a speed in m/s from a phase measured in radians or degrees. Use this relationship when proposed answers must distinguish a speed in m/s from a phase measured in radians or degrees..

Cambridge International AS & A Level Physics (9702) Unit 4 FAQ

Evidence workshop

Continue from the free model into complete practice

The full unit guide continues with the chapter’s worked examples, figures, scoring tables, and answer checks.

• Worked example: wave speed, phase and interference
• Waves and Superposition: change one condition
• Waves and Superposition: test proposed results
• Check the worked-example evidence for Waves and Superposition

Related Cambridge International AS & A Level Physics (9702) unit guides

How to study Cambridge International AS & A Level Physics (9702) Unit 4

Start with the organizing decision

Before solving, restate the decision in operational terms: Identify whether a horizontal axis is position or time before deciding whether its repeat spacing is wavelength or period.. Your first written move should be to Multiply 6.00 Hz by 0.240 m.

Practice the same idea in several representations

Rotate through A graph of displacement against position (m)., A formula card that explains speed uses frequency with wavelength, while phase uses path difference relative to wavelength., A table linking key concept, why it matters, visible method.. Use each representation to practice Progressive Waves: Wave Quantities, the Wave Equation and Intensity, Transverse and Longitudinal Waves and the Electromagnetic Spectrum, The Doppler Effect for Sound Waves, Polarisation and Malus's Law, Superposition and Stationary Waves, Diffraction and Two-Source Interference, The Diffraction Grating, and explain what stays invariant when the surface form changes.

Turn each error into a repair check

After every attempt, audit the response for Treating 0.180 m path difference as the wavelength; Reporting 0.750 as radians rather than cycles; Treating position as elapsed time. Then redo only the first step that made the reasoning diverge, keeping units, direction, and model conditions visible.

Confirm current course details in the official Cambridge International syllabus for the 2025-2027 administration.

Where to go next

Return to the Cambridge International AS & A Level Physics (9702) to see every unit and plan your revision.