Question

Which of the following is an example of the Doppler effect?

Vibrations from a tuning fork pass through the air and cause a nearby dish of
water to produce ripples of the same frequency.
Two identical musical instruments being played next to each other will produce a
sound twice as loud as if only one were played.
A hiker shouts "hello" into a canyon and hears it repeated back several times
before it fades away.
The siren of a police car sounds different when the car is coming toward you
than it does when it passes you.

Answer 1

The siren of a police car sounds different when the car is coming toward you

than it does when it passes you.

Step-by-step explanation:

The Doppler effect refers to the apparent change in the frequency of a sound wave when the distance between the source of the sound and the listener changes at a rapid pace. When a race car zooms past you, the change in the sound is very dramatic because of the rapid change in the distance between you and the source of the sound.

Answer 2

The siren of police car sounds different when the car is coming towards you than it does when it passes you.