Source
v = speed at the sound moves
1. What is meant by the Doppler Effect?
Audio 1
2. How does the frequency that the listener hears change :
2.1 if the car approaches him?
Audio 2.1
2.2 if the car moves away from him?
Audio 2.2
3. Write down the Doppler Equation.
4. What does each variable in the Doppler Equation mean?
fL = frequency the listener hears
vL = speed at which listener moves
fs = frequency the source emits
vs = speed at which source moves
5. How does the speed of the source affect the speed of the sound?
Assume a car was at rest and the siren emits a sound that moves at 330m.s-1.
The sound would still move at 330m.s-1 even if the car had been moving. It is only the frequency of the sound that gets affected.
Audio 5
6. A police car moves towards a listener at a speed of 20m.s-1.
The police sounds the siren at a frequency of 400Hz. The speed of the sound is 330m.s-1.
Calculate the frequency at which the listener will hear the siren.
7. A police car moves away from a listener at a speed of 30m.s-1.
The police sounds the siren at a frequency of 420Hz. The speed of the sound is 340m.s-1.
Calculate the frequency at which the listener will hear the siren.
8. A man runs at 5m.s-1 towards a police car which is approaching him at 10 m.s-1. The police siren emits a frequency of 450Hz.
Calculate the frequency at which the man will hear the siren if the speed of the sound is 340m.s-1.