This Great White Egret at Leighton Moss provided plenty of entertainment. I was interested in the circular ripples that emanated from its legs every time it moved. As it moved from left to right across the pond, the ripples started to bunch up in front of the bird and get spaced out behind. This is the same as the pattern I use in class:
In front of the movement the wavelength decreases and behind the wavelength increases. In front the frequency increases and behind it goes down. It's the old ambulance example: that the frequency of the siren is higher when it is coming towards to you and is lower than normal when it goes away. It is called the Doppler Effect.
