Progressive waves
Cambridge A-Level Physics (9702) · Unit 7: Waves · 10 flashcards
Progressive waves is topic 7.1 in the Cambridge A-Level Physics (9702) syllabus , positioned in Unit 7 — Waves , alongside Transverse and longitudinal waves, Doppler effect for sound waves and Electromagnetic spectrum. In one line: Wave motion is the transfer of energy through a medium (or vacuum) due to vibrations, without the transfer of the medium itself.
Marked as AS Level: examined at AS Level in Paper 1 (Multiple Choice), Paper 2 (AS Structured Questions) and Paper 3 (Advanced Practical Skills). The same content may also be assumed in Paper 4 (A Level Structured Questions).
The deck below contains 10 flashcards — 8 definitions and 2 key concepts — covering the precise wording mark schemes reward. Use the 8 definition cards to lock down command-word answers (define, state), then move on to the concept and calculation cards to handle explain, describe, calculate and compare questions.
Wave motion
Wave motion is the transfer of energy through a medium (or vacuum) due to vibrations, without the transfer of the medium itself.
What the Cambridge 9702 syllabus says
2025-2027 syllabus, in our words · AS LevelWhat the syllabus expects you to be able to do in this topic, in plain English. For the exact wording, see the official syllabus (PDF).
- Describe the meaning of wave motion, using the vibrations seen in ripple tanks, ropes and springs to illustrate it.
- Understand the terms speed, wavelength, frequency, period, amplitude, displacement and phase difference, and use them correctly.
- Understand how a CRO's (cathode-ray oscilloscope's) y-gain and time-base controls are used to measure amplitude and frequency.
- Starting from how wavelength, frequency and speed are defined, derive v = fλ, the wave equation.
- Recall v = fλ and use it.
- Understand that a progressive wave transfers energy.
- For a progressive wave, recall and use the relations intensity ∝ amplitude² and intensity = power / area.
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 9702 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Tips to avoid common mistakes in Progressive waves
- › Specify wavelength as the distance between two adjacent wavefronts or the minimum distance between points in phase.
- › Always use the relationship Intensity ∝ (Amplitude)² for any question involving the power or brightness of a wave.
Define wave motion.
Wave motion is the transfer of energy through a medium (or vacuum) due to vibrations, without the transfer of the medium itself.
Define 'displacement' in the context of wave motion.
Displacement is the distance of a point on a wave from its equilibrium position. It is a vector quantity.
Define 'amplitude' in the context of wave motion.
Amplitude is the maximum displacement of a point on a wave from its equilibrium position. It is linked to the energy carried: the intensity of a wave is proportional to amplitude squared.
Define 'phase difference'.
Phase difference is the fraction of a cycle (expressed in radians or degrees) between two points on a wave, or between two waves.
Define 'period' and 'frequency'.
Period (T) is the time taken for one complete oscillation. Frequency (f) is the number of complete oscillations per unit time (usually seconds). They are related by: f = 1/T.
Define 'wavelength'.
Wavelength (λ) is the distance between two successive points in phase on a wave.
Describe how to use a CRO to determine the frequency and amplitude of a wave.
The time-base setting on the CRO allows you to measure the period (T) of the wave. Frequency is then calculated as f = 1/T. The y-gain setting allows you to measure the peak voltage, which is directly related to the wave's amplitude.
State the wave equation and define each term.
The wave equation is v = fλ, where v is the wave speed (m/s), f is the frequency (Hz), and λ is the wavelength (m).
How is intensity related to amplitude for a progressive wave?
Intensity is directly proportional to the square of the amplitude: Intensity ∝ (amplitude)². This means if amplitude doubles, intensity quadruples.
Define Intensity of a wave.
Intensity is defined as the power transmitted per unit area, where the area is perpendicular to the direction of wave propagation. Intensity = Power/Area.
Review the material
Read full revision notes on Progressive waves — definitions, equations, common mistakes, and exam tips.
Read NotesMore topics in Unit 7 — Waves
Progressive waves sits alongside these A-Level Physics decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Key terms covered in this Progressive waves deck
Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.
How to study this Progressive waves deck
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