How Does Sonar Work?

Google RADAR and SONAR, they work in a similar fashion...
It's too difficult to explain in detail here but basically you send out a short pulse of sound or radiation, and then receive the return 'echo'. the time to the echo gives distance and the direction in which the pulse was transmitted gives direction.
Thus if you sweep the transmitter round and round or back and forth (like a TV frame/line scan) you can build up a picture.
Del
_{(JohnDG will probably insist it's all to do with string) (in house joke)}

http://en.wikipedia.org/wiki/Sonar