CAIE A-Level Physics 7.1.4 Derivation of v = fλ

Practise deriving v = f lambda from wave-speed definitions, explaining assumptions, units and the link between period and frequency.

Exam points

derive v = fλ from the definitions of wave speed, frequency and wavelength
explain the assumptions and units in the wave equation and connect period with frequency

[Maximum number: 1]

A loudspeaker oscillates with frequency f to produce sound waves of wavelength $\lambda$ . The loudspeaker makes N oscillations in time t.

Use your answers in (i) to deduce the equation relating the speed v of the sound wave to f and $\lambda$ .

v(= distance / time $)=N \lambda /(N / f)$ so $v=f \lambda$

B1

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