/rez"euh neuhns/, n.1. the state or quality of being resonant.2. the prolongation of sound by reflection; reverberation.3. Phonet.a. amplification of the range of audibility of any source of speech sounds, esp. of phonation, by various couplings of the cavities of the mouth, nose, sinuses, larynx, pharynx, and upper thorax, and, to some extent, by the skeletal structure of the head and upper chest.b. the distribution of amplitudes among interrelated cavities in the head, chest, and throat that are characteristic for a particular speech sound and relatively independent of variations in pitch.4. Physics.a. the state of a system in which an abnormally large vibration is produced in response to an external stimulus, occurring when the frequency of the stimulus is the same, or nearly the same, as the natural vibration frequency of the system.b. the vibration produced in such a state.c. a hadron with a very short lifetime, of the order of 10-23 sec.5. Elect. that condition of a circuit with respect to a given frequency or the like in which the net reactance is zero and the current flow a maximum.6. Also called mesomerism. Chem. the condition exhibited by a molecule when the actual arrangement of its valence electrons is intermediate between two or more arrangements having nearly the same energy, and the positions of the atomic nuclei are identical.7. Med. (in percussing for diagnostic purposes) a sound produced when air is present.[1485-95; < MF < L resonantia echo, equiv. to reson(are) to RESOUND + -antia -ANCE]
* * *IIn physics, the relatively large selective response of an object or a system that vibrates in step with an externally applied vibration.Acoustical resonance is the vibration induced in a string of a given pitch when a note of the same pitch is produced nearby, in the sound box of an instrument such as a guitar, or in the mouth or nasal cavity when speaking. Mechanical resonance, such as that produced in a bridge by wind or by marching soldiers, can eventually produce wide swings great enough to cause the bridge's destruction. Resonance in frequency-sensitive electrical circuits makes it possible for certain communication devices to accept signals of some frequencies while rejecting others. Magnetic resonance occurs when electrons or atomic nuclei respond to the application of magnetic fields by emitting or absorbing electromagnetic radiation. See also nuclear magnetic resonance.II(as used in expressions)electron paramagnetic resonance EPR
* * *in particle physics, an extremely short-lived phenomenon associated with subatomic particles called hadrons (hadron) that decay via the strong nuclear force (strong force). This force is so powerful that it allows resonances to exist only for the amount of time it takes light to cross each such “object.” A resonance occurs when the net energy of the colliding subatomic particles is just enough to produce its rest mass, which the strong force then causes to disintegrate within 10-23 second.in physics, relatively large selective response of an object or a system that vibrates in step or phase, with an externally applied oscillatory force. Resonance was first investigated in acoustical systems such as musical instruments and the human voice. An example of acoustical resonance is the vibration induced in a violin or piano string of a given pitch when a musical note of the same pitch is sung or played nearby.The concept of resonance has been extended by analogy to certain mechanical and electrical phenomena. Mechanical resonance, such as that produced in bridges by wind or by marching soldiers, is known to have built up to proportions large enough to be destructive, as in the case of the destruction of the Tacoma Narrows Bridge (q.v.) in 1940. Spacecraft, aircraft, and surface vehicles must be designed so that the vibrations caused by their engines or by their movement through air are kept to a safe minimum.Resonance in electrical systems is of a somewhat different nature. Its occurrence in frequency-sensitive (alternating-current) circuits makes it possible for communication devices equipped with such circuits to accept signals of certain frequencies while rejecting others. In a television receiver, for example, resonance occurs when the frequency of one of the incoming signals reaching the circuit is near the natural frequency of the circuit, which then responds by absorbing maximum energy from the signal as the current within the circuit surges back and forth in step with the very weak current in the antenna.A form of resonance somewhat analogous to a certain kind of mechanical resonance has been detected on the nuclear scale. This phenomenon, called magnetic resonance, occurs when atoms or their nuclei respond to the application of various magnetic fields by emitting or absorbing electromagnetic radiation of radio and microwave frequencies. See also magnetic resonance.
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