doppler

In this picture, the ducks are swimming through the water and making waves. Since the duck is swimming faster than the wave it is creating it will all pile up in front of the duck. This piling of waves is called the Doppler effect. This happens with sound waves also. When a car moves toward you, the frequency changes because of the pile up of waves. Breaking the sound barrier was achieved when airplane designers put a point of the plane. Once an object moves faster than the sound waves it produces the waves make a v shaped behind the object. This is seen in the picture.