QUESTION 4 In the diagram, a vehicle with a siren attached to its roof is travelling to the right. The siren
emits a continuous note of frequency 450 Hz. Upon listening to a recording on the tape
recorder, the siren appeared to be emitting 2 sounds of different frequencies, 464 Hz and
437 Hz.
towards and
away
Emitted sound
Tape Recorder
4.1 Name the phenomenon which would have led to the recording of the two
different notes.
(1)
4.2 State and very briefly describe one useful application of this phenomenon
(as it applies to sound or light).
(3)
4.3 Use the information in the text to determine the magnitude of the velocity
at which the vehicle was travelling.
Take the speed of sound to be 340 m. s.
(4)
4.4.
Explain (in terms of the wave fronts being produced) why the observed frequencies
are respectively higher and lower than the frequency of the source. (4)