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Resonance — Journal of Science Education is now distributed in print outside India and online worldwide by Springer , co-publisher of the journal together with the Indian Academy of Sciences. Print subscriptions within India and open online access will continue to be served from Indian Academy of Sciences.
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Current Issue Volume 24 Issue 9 September Contact Site index. Toggle navigation Indian Academy of Sciences. When damping is small, the resonant frequency is approximately equal to the natural frequency of the system, which is a frequency of unforced vibrations. Some systems have multiple, distinct, resonant frequencies. A familiar example is a playground swing , which acts as a pendulum.
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Pushing a person in a swing in time with the natural interval of the swing its resonant frequency makes the swing go higher and higher maximum amplitude , while attempts to push the swing at a faster or slower tempo produce smaller arcs. This is because the energy the swing absorbs is maximized when the pushes match the swing's natural oscillations. Resonance occurs widely in nature, and is exploited in many manmade devices. It is the mechanism by which virtually all sinusoidal waves and vibrations are generated. Many sounds we hear, such as when hard objects of metal , glass , or wood are struck, are caused by brief resonant vibrations in the object.
Light and other short wavelength electromagnetic radiation is produced by resonance on an atomic scale , such as electrons in atoms. Other examples of resonance:. The dramatically visible, rhythmic twisting that resulted in the collapse of "Galloping Gertie", the original Tacoma Narrows Bridge , is mistakenly characterized as an example of resonance phenomenon in certain textbooks.
Robert H. Scanlan , father of bridge aerodynamics , has written an article about this misunderstanding. Ordinarily, uploaded parameters for controlling the engine control system for the Zvezda module make the rocket engines boost the International Space Station to a higher orbit. The rocket engines are hinge -mounted, and ordinarily the crew doesn't notice the operation.
On January 14, , however, the uploaded parameters made the autopilot swing the rocket engines in larger and larger oscillations, at a frequency of 0. These oscillations were captured on video, and lasted for seconds. Mechanical resonance is the tendency of a mechanical system to absorb more energy when the frequency of its oscillations matches the system's natural frequency of vibration than it does at other frequencies.
It may cause violent swaying motions and even catastrophic failure in improperly constructed structures including bridges, buildings, trains, and aircraft. When designing objects, engineers must ensure the mechanical resonance frequencies of the component parts do not match driving vibrational frequencies of motors or other oscillating parts, a phenomenon known as resonance disaster. Avoiding resonance disasters is a major concern in every building, tower, and bridge construction project.
As a countermeasure, shock mounts can be installed to absorb resonant frequencies and thus dissipate the absorbed energy. The Taipei building relies on a tonne pendulum short-ton —a tuned mass damper —to cancel resonance. Furthermore, the structure is designed to resonate at a frequency that does not typically occur.
Buildings in seismic zones are often constructed to take into account the oscillating frequencies of expected ground motion. In addition, engineers designing objects having engines must ensure that the mechanical resonant frequencies of the component parts do not match driving vibrational frequencies of the motors or other strongly oscillating parts.
Clocks keep time by mechanical resonance in a balance wheel , pendulum , or quartz crystal. The cadence of runners has been hypothesized to be energetically favorable due to resonance between the elastic energy stored in the lower limb and the mass of the runner. Acoustic resonance is a branch of mechanical resonance that is concerned with the mechanical vibrations across the frequency range of human hearing, in other words sound. This is the source of many percussive sounds we hear. Acoustic resonance is an important consideration for instrument builders, as most acoustic instruments use resonators , such as the strings and body of a violin , the length of tube in a flute , and the shape of, and tension on, a drum membrane.
Like mechanical resonance, acoustic resonance can result in catastrophic failure of the object at resonance. The classic example of this is breaking a wine glass with sound at the precise resonant frequency of the glass, although this is difficult in practice. Electrical resonance occurs in an electric circuit at a particular resonant frequency when the impedance of the circuit is at a minimum in a series circuit or at maximum in a parallel circuit usually when the transfer function peaks in absolute value. Resonance in circuits are used for both transmitting and receiving wireless communications such as television, cell phones and radio.
An optical cavity , also called an optical resonator , is an arrangement of mirrors that forms a standing wave cavity resonator for light waves. Optical cavities are a major component of lasers , surrounding the gain medium and providing feedback of the laser light. They are also used in optical parametric oscillators and some interferometers. Light confined in the cavity reflects multiple times producing standing waves for certain resonant frequencies.
The standing wave patterns produced are called "modes". Longitudinal modes differ only in frequency while transverse modes differ for different frequencies and have different intensity patterns across the cross-section of the beam. Ring resonators and whispering galleries are examples of optical resonators that do not form standing waves. Different resonator types are distinguished by the focal lengths of the two mirrors and the distance between them; flat mirrors are not often used because of the difficulty of aligning them precisely. The geometry resonator type must be chosen so the beam remains stable, i.
Resonator types are also designed to meet other criteria such as minimum beam waist or having no focal point and therefore intense light at that point inside the cavity. Optical cavities are designed to have a very large Q factor. Additional optical resonances are guided-mode resonances and surface plasmon resonance , which result in anomalous reflection and high evanescent fields at resonance.
In this case, the resonant modes are guided modes of a waveguide or surface plasmon modes of a dielectric-metallic interface. These modes are usually excited by a subwavelength grating. In celestial mechanics , an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers. Orbital resonances greatly enhance the mutual gravitational influence of the bodies.
In most cases, this results in an unstable interaction, in which the bodies exchange momentum and shift orbits until the resonance no longer exists. Under some circumstances, a resonant system can be stable and self-correcting, so that the bodies remain in resonance. Examples are the resonance of Jupiter 's moons Ganymede , Europa , and Io , and the resonance between Pluto and Neptune.
Unstable resonances with Saturn 's inner moons give rise to gaps in the rings of Saturn. The special case of resonance between bodies with similar orbital radii causes large Solar System bodies to clear the neighborhood around their orbits by ejecting nearly everything else around them; this effect is used in the current definition of a planet. Nuclear magnetic resonance NMR is the name given to a physical resonance phenomenon involving the observation of specific quantum mechanical magnetic properties of an atomic nucleus in the presence of an applied, external magnetic field.
Many scientific techniques exploit NMR phenomena to study molecular physics , crystals , and non-crystalline materials through NMR spectroscopy. NMR is also routinely used in advanced medical imaging techniques, such as in magnetic resonance imaging MRI.
All nuclei containing odd numbers of nucleons have an intrinsic magnetic moment and angular momentum. A key feature of NMR is that the resonant frequency of a particular substance is directly proportional to the strength of the applied magnetic field. It is this feature that is exploited in imaging techniques; if a sample is placed in a non-uniform magnetic field then the resonant frequencies of the sample's nuclei depend on where in the field they are located.
Therefore, the particle can be located quite precisely by its resonant frequency. Electron paramagnetic resonance , otherwise known as electron spin resonance ESR , is a spectroscopic technique similar to NMR, but uses unpaired electrons instead. Materials for which this can be applied are much more limited since the material needs to both have an unpaired spin and be paramagnetic. Resonance in particle physics appears in similar circumstances to classical physics at the level of quantum mechanics and quantum field theory.
The formula is further related to the particle's decay rate by the optical theorem. The exact response of a resonance, especially for frequencies far from the resonant frequency, depends on the details of the physical system, and is usually not exactly symmetric about the resonant frequency, as illustrated for the simple harmonic oscillator above.
The intensity is defined as the square of the amplitude of the oscillations. This is a Lorentzian function , or Cauchy distribution , and this response is found in many physical situations involving resonant systems. Heavily damped oscillators tend to have broad linewidths, and respond to a wider range of driving frequencies around the resonant frequency.
The linewidth is inversely proportional to the Q factor , which is a measure of the sharpness of the resonance. In radio engineering and electronics engineering , this approximate symmetric response is known as the universal resonance curve , a concept introduced by Frederick E. Terman in to simplify the approximate analysis of radio circuits with a range of center frequencies and Q values.
A physical system can have as many resonant frequencies as it has degrees of freedom ; each degree of freedom can vibrate as a harmonic oscillator. Systems with one degree of freedom, such as a mass on a spring, pendulums , balance wheels , and LC tuned circuits have one resonant frequency.
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Systems with two degrees of freedom, such as coupled pendulums and resonant transformers can have two resonant frequencies. As the number of coupled harmonic oscillators grows, the time it takes to transfer energy from one to the next becomes significant. The vibrations in them begin to travel through the coupled harmonic oscillators in waves, from one oscillator to the next.
Extended objects that can experience resonance due to vibrations inside them are called resonators , such as organ pipes , vibrating strings , quartz crystals , microwave and laser cavities. Since these can be viewed as being made of many coupled moving parts such as atoms , they can have correspondingly many resonant frequencies.
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