Resonance in open pipes
Resonance may be obtained with a tuning fork and a pipe open at both ends, in
which case there is an antinode at each end and a node in the middle. Bearing this in mind, we should expect the shortest length of open pipe which resonates to a given fork to be twice as long as the shortest closed pipe.
This assumption may be verified by the use of two tubes, one of which slides inside the other with a nice fit. Starting with this composite tube at its shortest length, the inner tube is gradually pulled out until resonance is obtained with a vibrating fork held near one end. The length is found to be double that of the shortest closed tube which resonates to the same fork (Fig. 29.10).