The Doppler effect is the change in frequency of a wave (sound or light) experienced by an observer relative to its moving source. One of the most routine examples of the Doppler effect occurs when the frequency of the sound of an approaching vehicle is higher, and then drops to a lower frequency when the vehicle is travelling farther away. The phenomena is sometimes referred to as Doppler shift, highlighting the way the forward or backward travel of a wave-emitting source causes shifts in the frequency of the waves as experienced by an observer.
Brain on Board
Your brain is your vehicle's most important safety feature.
