A-LevelPhysicsWaves9702/21 · May/June 2017 · Q54 Marks
Describe the Doppler effect.
- (a)Describe the Doppler effect.[1]
- (b)A car travels with a constant velocity along a straight road. The car horn with a frequency of 400 Hz is sounded continuously. A stationary observer on the roadside hears the sound from the horn at a frequency of 360 Hz. The speed of sound is 340 m s⁻¹. Determine the magnitude v, and the direction, of the velocity of the car relative to the observer.[3]
Mark scheme
Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.
- [B1] observed frequency is different to source frequency when source moves relative to observer
- [C1] 360 = (400 × 340) / (340 ± v)
- [A1] v = 38 (37.8) m s¯¹
- [B1] away (from the observer)
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