Question

a police car is speeding north with its siren blaring. the sound waves from the siren increase in frequency
a north of the car.
b south of the car.
c in all directions around the car.
d none of the above

Explanation:

This problem is related to the Doppler effect. When a source (the police - car siren) is moving, the frequency of the waves changes for an observer. For an observer in front of the moving source (north of the car in this case, as the car is moving north), the wavelength of the sound waves is compressed. According to the formula \(f=\frac{v}{\lambda}\) (where \(v\) is the speed of sound and \(\lambda\) is the wavelength), a decrease in wavelength \(\lambda\) leads to an increase in frequency \(f\). For an observer behind the source (south of the car), the wavelength is stretched, so the frequency decreases.

Answer:

A. north of the car.