The Doppler Effect

The Doppler Effect

Observing the doppler effect......You are observing the pitch of a motorbike engine.....

If the observer and motorbike remain stationary the pitch of the sound remains the same. 

If the observer stands still and the motor bike is moving along a road as it approaches the pitch is higher.

After the motobike passes the observer the pitch becomes lower.

This happens because the motorcycle moving forward compresses the airwaves ahead of it increasing the pitch of sound.