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LearnCambridge97022025–2027Paper 2 · AS Level Structured QuestionsWaves

Paper 2 · Module

Waves

3 subtopics≈ 95 min in total

Start the module: Progressive waves and intensity Open graphing calculator

Progressive waves and intensity
A progressive wave transfers energy without transferring matter. Points one wavelength apart oscillate in phase; points half a wavelength apart are in antiphase. Phase difference (in degrees or radians) $=\dfrac{x}{\lambda}\times360^\circ$ . Intensity, the power per unit area, is proportional to amplitude squared, and falls with the inverse square of distance from a point source.
≈ 35 min
The Doppler effect
When a sound source moves, its wavefronts bunch up in front and spread out behind. A stationary observer in front receives a shorter wavelength and a higher frequency; behind, a longer wavelength and lower frequency. For a source moving at $v_s$ towards or away from you, $f_o=\dfrac{f_sv}{v\mp v_s}$ .
≈ 30 min
Electromagnetic spectrum and polarisation
All electromagnetic waves are transverse and travel at $3.00\times10^8$ m s⁻¹ in free space. Wavelengths run from kilometres (radio) to less than $10^{-11}$ m (gamma); visible light is $400$ – $700$ nm. Only transverse waves can be polarised. A polariser halves unpolarised light; after that, Malus's law gives $I=I_0\cos^2\theta$ .
≈ 30 min