Physics (AS & A Level) · Oct / Nov 2016 · Paper 21 · Question 4

the number of oscillations per unit time of the source/of a point on the wave/of a particle (in the medium) [2]

or the number of wavelengths/wavefronts per unit time (M1) passing a (fixed) point (A1)

T or period = 2.5 × 250 (µs) (= 625 µs) frequency = 1 / (6.25 × 10–4) or 1 / (2.5 × 250 × 10–6) = 1600 Hz [2]

for maximum frequency: fo = fsv / (v – vs) 1640 = (1600 × 330) / (330 – vs) vs = 8(.0) m s–1 (8.049 m s–1) [2]

loudspeaker moving towards observer causes rise in/higher frequency loudspeaker moving away from observer causes fall in/lower frequency [2]

or repeated rise and fall/higher and then lower frequency (M1) caused by loudspeaker moving towards and away from observer (A1)