Question

if you are standing a few blocks north of the police car with its siren blaring, how does its siren sound to you as the car gets closer to your location? a the sirens pitch gets lower. b the sirens pitch gets lower and then higher. c the sirens pitch does not change. d the sirens pitch gets higher.

Explanation:

This problem involves the Doppler effect in physics. The Doppler effect describes the change in frequency (and thus pitch) of a wave (such as sound) due to the relative motion between the source of the wave and the observer. When the police car (the source of the sound - the siren) is moving towards the observer (you), the frequency of the sound waves received by the observer increases. Since pitch is related to the frequency of sound (higher frequency means higher pitch), as the car gets closer, the siren’s pitch gets higher.

Answer:

d. The siren’s pitch gets higher.