ETYM Cf. French résonance, Latin resonantia an echo.
Rapid and uncontrolled increase in the size of a vibration when the vibrating object is subject to a force varying at its natural frequency. In a trombone, for example, the length of the air column in the instrument is adjusted until it resonates with the note being sounded. Resonance effects are also produced by many electrical circuits. Tuning a radio, for example, is done by adjusting the natural frequency of the receiver circuit until it coincides with the frequency of the radio waves falling on the aerial.
Resonance has many physical applications. Children use it to increase the size of the movement on a swing, by giving a push at the same point during each swing. Soldiers marching across a bridge in step could cause the bridge to vibrate violently if the frequency of their steps coincided with its natural frequency.
Resonance was the cause of the collapse of the Tacoma Narrows bridge, us, in 1940, when the frequency of the wind coincided with the natural frequency of the bridge.
1. A vibration of large amplitude produced by a relatively small vibration near the same frequency of vibration as the natural frequency of the resonating system.
2. An excited state of a stable particle causing a sharp maximum in the probability of absorption of electromagnetic radiation.