Physics 9702 · AS & A Level · Progressive waves

Progressive waves — practice question

A sound source emits sound with frequency $f$. It produces sound of wavelength $\lambda$.
(a(i)1)[1]

State the meaning of the frequency of the source.

(a(i)2)[1]

State the distance travelled, in terms of $\lambda$, by a wavefront after $n$ oscillations of the source.

(a(ii))[2]

Using your answers in (i), deduce an expression for the wave speed $v$ in terms of $f$ and $\lambda$.

(b(i))[2]

Fig. 5.1 shows the waveform of a sound wave displayed on the screen of a cathode-ray oscilloscope (c.r.o.). The time-base setting of the c.r.o. is $2.0\ \text{ms cm}^{-1}$. Determine the frequency of the sound wave.

(b(ii))[1]

A second sound wave has the same frequency as that found in (i). Both waves have the same amplitude, but the phase difference between them is $90^\circ$. On Fig. 5.1, sketch the waveform of this second wave.

(i)[2]

Determine the frequency of the sound wave.

(ii)[1]

A second sound wave has the same frequency as that found in (i). The amplitude of the two waves is the same, but the phase difference between them is $90^\circ$. On Fig. 5.1, draw the waveform of this second wave.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: count of oscillations per unit time (not per second)

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