The New Student's Reference Work/Resonance
Resonance (rĕz′ō̇-năns), in physics the process by which one body sets in vibration another body having the same period of vibration. When one attempts to ring a large church-bell, he soon learns that he must pull the rope at certain definite intervals if he wishes to ring with ease. A rowboat moored in quiet water can, without difficulty, be set rocking if one throw his weight, first on one side then on the other, at correct intervals. If two pendulums of the same period be mounted upon one common frame, and then one pendulum be set in vibration while the second is at rest, the second pendulum, soon “picks up” a vibration of considerable amplitude from the first pendulum. These are instances of resonance, taken from mechanics. In acoustics and electricity there also are many illustrations. A tuning-fork held over a tall jar partially filled with water will have its sound much reinforced when the column of air in the jar above the water is capable of vibrating in the same period as the tuning-fork. The sounding-box of the guitar and violin are in resonance with the strings and enable them to give out energy at a more rapid rate. Electrical resonance is frequently employed in wireless telegraphy. For a complete theory of resonance see Donkin's Acoustics.