2. Frequency is the:
A. maximum amplitude of a sound wave
B. number of vibrations per second
C. duration of each and every successive wave
D. distance between two consecutive points in phase

3.1. What is meant by the Doppler Effect?
3.2. Does the Doppler Effect occur only for sound waves?
3.3. Does the Doppler Effect occur for transverse waves?

4. Write down the Doppler Equation for sound waves, and state what each symbol means.

5. A police-car is moving towards you with its siren on.
5.1. Would you expect to hear a higher or lower frequency of sound? Explain
5.2. Would the wavelength of the sound that you hear be greater or lesser than at the source?

6. A police car is stationary some distance away from a stationary listener. The police sounds the siren at a frequency of 400Hz.
The speed of the sound is 335ms^-1 .

6.1. What is meant by the term frequency of 400Hz?

6.2. At what frequency will the listener hear the siren?

6.3. Now the police car moves towards the listener at a speed of 22ms^-1.

6.3.1. What would be the speed of the sound when the police car moves at 22ms^-1 towards the listener?

6.3.2. Calculate the frequency at which the listener will hear the siren.

6.3.3. Why is the frequency different from the actual frequency of the emitted siren?

6.3.4. At what frequency will the listener hear the siren if the police car was moving away from him at a speed of 22ms^-1?

7. A car is moving at an unknown speed towards a stationary listener in a 60km.h^-1 zone. The car emits a siren at a frequency of 430Hz, and the speed of the sound is 330ms^-1. The listener records that he hears frequency of the sound at 426Hz.

7.1. Calculate the speed of the car in ms^-1.

7.2. Is the car breaking the speed limit?

8. A police-car moves towards a listener at a speed of 30ms^-1 and emits a siren with a wavelength of 1,2m.
The speed of the sound is 340ms^-1. The listener moves directly towards the police-car at a speed of 4ms^-1.

8.1. What is meant by the term wavelength?

8.2. Are sound waves longitudinal or transverse?

8.3. Calculate the frequency of the siren at the source.

8.4. Calculate the period of the siren sound.

8.5. At what frequency will the listener hear the siren?

8.6. What should be the velocity of the listener in order for him to hear the frequency of the siren at the real frequency? Explain.