Show model answer and explanation
10
v = 5 × 2.
A Level · English Medium · Pearson Edexcel · Physics
Waves, light and sound
Relate wave speed, frequency, refraction and interference.
Shared cross-level core and stretch unit. Start with the core questions, then use the stretch example for deeper work. The same unit is available in related class and board pathways; it is not a full grade-specific or examination-specification course. A teacher should select the appropriate depth and further topics.
Learn the idea
Wave speed v = fλ links frequency f and wavelength λ. Frequency counts cycles per second. A wave crossing into a different medium keeps its frequency while speed and wavelength can change. Superposition adds displacements where waves overlap; persistent interference also requires an appropriate phase relationship.
Worked example
A wave at 50 Hz with wavelength 0.4 m travels at 20 m/s. If its speed becomes 10 m/s in a new medium, its unchanged 50 Hz frequency gives wavelength 0.2 m.
- Identify the medium and quantities.
- Keep frequency fixed across a stationary boundary.
- Explain the physical relationship as well as the calculation.
Stretch example
For double-slit light interference at small angles, fringe spacing w = λD/a. With λ = 500 nm, D = 2 m and a = 0.5 mm, w = 0.002 m = 2 mm.
Your written practice
Show your working on paper and enter your answer here. If it does not match, compare the model and try again.
Show model answer and explanation
170
f = v/λ.
Show model answer and explanation
yes
Sound is a mechanical wave.
Write in your own words. A guardian or teacher should review this response.
Show model answer and explanation
Transverse displacement is perpendicular to propagation; longitudinal displacement is parallel.
Compare direction of oscillation with propagation.
Write in your own words. A guardian or teacher should review this response.
Show model answer and explanation
Light is electromagnetic; sound needs mechanical interactions in matter.
Identify the different mechanisms.
Show model answer and explanation
2
Spacing is directly proportional to D.
Write in your own words. A guardian or teacher should review this response.
Show model answer and explanation
Sources need the same frequency and a stable phase difference; the setup must allow overlapping waves.
Mention coherence and overlap; practical visibility can need comparable amplitudes.
Wave diagram
Draw two labelled wave profiles and explain one constructive and one destructive overlap.
Review with a guardian or teacher
- Use displacement axes.
- State relative phase.
- Distinguish a diagram from an actual measurement.
Keep your work on paper or in a local file. This page does not upload it or automatically grade the project.
Teacher-led lessons, schedules and prices for this outline are upcoming. You can use any starter practice above now without booking.
Your next step
Solo practice works without an account. Sign in to save a practice record to your learner profile.
Keep practising
Exact lesson links and related activities are labelled separately. Return-to-course links retain your selected learning path.