Question

Have you heard an ambulance, police car, or fire truck recently? Did you notice that the pitch of the siren changed as it approached you and then again as it moved away? What concept explains this change or shift in sound waves?

Answer 1

The Doppler Effect is the change in frequency or wavelength of a wave for an observer moving relative to its source. It is named after the Austrian physicist Christian Doppler.

Answer 2

Answer: Doppler effect

Explanation:

When there is relative motion between source and listener of sound, the apparent frequency heard by the listener is different from the frequency of the source. When the source and the listener are moving closer, the apparent frequency increases and when they move apart, there is decrease in the apparent frequency. This is Doppler's effect.

The wave-fronts move closer as the source and listener approach closer to each other. Thus, the observed frequency is greater than the actual. The pitch depends on frequency, greater is the pitch.