9702 · 7.1
Progressive waves flashcards
Revision flashcards for Cambridge 9702 Progressive waves (syllabus 7.1). Flip, recall, then mark a real past-paper question.
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What is a progressive wave's primary role?
To transmit energy from one point to another without transferring matter.
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Define Amplitude (A).
The maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position.
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How are frequency and period related?
Frequency ($f$) is the inverse of the period ($T$), so $f = 1/T$.
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What is the fundamental wave equation?
Wave speed ($v$) = frequency ($f$) \times wavelength ($\lambda$), or $v = f\lambda$.
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What distinguishes a transverse wave?
Particle oscillations are perpendicular to the direction of energy transfer.
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Give an example of a longitudinal wave.
Sound waves are a common example, involving compressions and rarefactions.
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What is phase difference?
It describes the difference in oscillatory state between two points on a wave, measured in degrees or radians. It is the fraction of a cycle by which one oscillation leads or lags another.
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How does wave intensity relate to amplitude?
Wave intensity ($I$) is directly proportional to the square of its amplitude ($A$), so $I \propto A^2$.
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What phenomenon proves a wave is transverse?
Polarisation, which restricts wave oscillations to a single plane, can only occur with transverse waves.
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What is the Doppler effect?
The perceived change in frequency and wavelength of a wave due to relative motion between its source and the observer.
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Can EM waves travel through a vacuum?
Yes, all electromagnetic waves are transverse and can travel through a vacuum at the speed of light ($c \approx 3.00 \times 10^8 \text{ ms}^{-1}$).
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What can be determined from a displacement-distance graph of a wave?
The wave's amplitude (A) and its wavelength (λ).
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What can be determined from a displacement-time graph of a wave?
The wave's amplitude (A) and its period (T), from which frequency can be calculated ($f=1/T$).
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What does it mean for two points on a wave to be 'in antiphase'?
They have a phase difference of $\pi$ radians (or 180°). They are at equal and opposite displacements from equilibrium and moving in opposite directions.