The pitch of the siren of a moving fire truck changed from high to low as the fire truck basses by. What property of a sound wave changes as the fire truck goes by?

Question

anonymous · Answer

The Doppler effect. The sped of sound is essentially fixed in the air, the shorter the wavelength the higher the pitch. Because the truck is moving the same direction of the sound the wavelengths are getting closer together. the speed of the sound does not change in this example.