9702 · 7.2
Transverse and longitudinal waves flashcards
Revision flashcards for Cambridge 9702 Transverse and longitudinal waves (syllabus 7.2). Flip, recall, then mark a real past-paper question.
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What is the key difference in particle oscillation relative to energy transfer for transverse versus longitudinal waves?
In transverse waves, particles oscillate perpendicular to energy transfer; in longitudinal waves, they oscillate parallel.
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Can sound waves undergo polarisation, and why/why not?
No, sound waves cannot be polarised because they are longitudinal waves, meaning their oscillations are parallel to the direction of energy transfer and cannot be restricted to a single plane.
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Name two examples of transverse waves and one example of a longitudinal wave.
Transverse waves: Light (or any EM wave), waves on a string. Longitudinal wave: Sound waves.
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State the relationship between a wave's speed, frequency, and wavelength.
The wave speed (v) is equal to the product of its frequency (f) and wavelength (λ): v = fλ.
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What characteristic of a wave is proven by its ability to be polarised?
Its transverse nature.
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Define wavelength (λ).
The distance between two consecutive corresponding points on a wave, such as two peaks of a transverse wave or two compressions of a longitudinal wave.
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What is frequency (f)?
The number of complete wave cycles or oscillations that pass a fixed point per second, measured in Hertz (Hz).
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How is the period (T) of a wave related to its frequency (f)?
Period is the time for one complete oscillation and is the inverse of frequency: T = 1/f.
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What is a medium, and which type of wave requires one for transmission?
A medium is a substance (solid, liquid, or gas) through which waves travel. Longitudinal waves typically require a medium.
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State Malus' Law for the intensity of a polarised wave after passing through a filter.
I = I₀cos²θ, where I₀ is initial intensity, I is final intensity, and θ is the angle between the wave's plane of oscillation and the polariser's axis.
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How is the intensity (I) of any wave related to its amplitude (A)?
The intensity of a wave is proportional to the square of its amplitude: I \propto A^2.