Imagine a vibrating rod in the water If the rod had been vibrating In one place we would have seen Concentric circles centered on the same point But since the source of the waves is moving The wavelenght is shortened on one side And the kenghted on the other. This is known as the doppler effect In the airplanes this effect Is very cool in the speed of sound, Also known as match one, An explosion cuting the air Sonic boom! Crushing the glasses. Sonic boom! Cuting the air Sonic boom!