After an approaching ambulance passes a stationary observer, what does the frequency of the sound of the siren heard by the observer appear to do?

1 Answer
Jan 22, 2016

The frequency of the siren decreases.


This is known as doppler effect.

The wavefronts get more spread out as the relative speed between the sound waves propagating towards the observer and the ambulance increases.

Therefore, there will be a longer time interval between successive wavefronts.