# Resonance Meaning - Amplitude Definition, Frequency, Real-Life Examples and Applications

## Amplitude

The maximum extent to which the vibrating waves in a particular medium move and come back to the measured point of equilibrium (rest) is known as amplitude.

The energy associated with a wave is directly proportional to that its amplitude. Therefore, the higher the amplitude, the higher is the energy and vice versa. Also, the square of the amplitude is proportional to the intensity of the wave. Since amplitude is the displacement covered by the particle/wave, the SI unit of it is m (meter). However, the logarithm of the square of amplitude is usually quoted in dB (decibel).

## Frequency

To put it simply, frequency is defined as the number of times a wave in periodic motion vibrates in unit time. This unit time, taken by a wave to vibrate in a said frequency, is called one cycle of that system. Because of this, frequency is inversely proportional to time, given by its equation f=1/t. Frequency is measured in Hz (hertz).

## Resonance

Resonance is the process by which the amplitude of a dynamic system is increased by applying a periodic force that has its frequency value approximately the same or equal to the frequency of the system the force is made to act on. If the same periodic force is applied to the system at any other frequency that does not match that of the system, the amplitude value will not increase. The frequency at which the system has a relative maximum amplitude is known as the resonance frequency of that system. Some systems have multiple, distinct, resonant frequencies. The word resonance is derived from the Latin term resonantia, which means ‘to sound again’. There is a loss in energy of the vibrating wave with each cycle, which is called damping. Since the phenomenon of resonance occurs in all types of vibrations or waves, there are different types of resonances like

• Mechanical resonance – This occurs in mechanical systems and concrete structures. It can lead to disastrous swaying and the destruction of that structures. Thus, it is called resonance disaster.
• Acoustic resonance – It is a phenomenon predominantly employed in musical instruments where sound waves with a particular matching frequency are amplified.
• Electromagnetic resonance is the kind of resonance that occurs in electromagnetic waves, such as microwaves, infrared, ultraviolet, gamma rays, and more.
• Nuclear magnetic resonance – It occurs when a nucleus in a strong magnetic field is disturbed by a nearby weak oscillating magnetic field and reacts to this by producing an electromagnetic wave of a frequency that matches that of the strong magnetic field.

## Real-Life Examples of Resonance

• The phenomenon of resonance can be visually seen when an opera singer sings at a particular “loudness”, holding a cup made of glass. The frequency at which the singer sings eventually matches that of the resonant frequency of the glass cup, and it ends up shattering.
• In a pendulum, when the weight is pushed with a certain force exactly as it comes to its position of rest, the pendulum picks up speed. Again, this is because the force, which in this case is the resonant frequency, increases the height achieved by the pendulum, which is the amplitude.
• Quartz clocks have an electronic oscillator regulated by a quartz crystal, which can produce very precise frequencies. This will equate to the movement of various hands in the clocks.
• In 1831, when a battalion of soldiers were marching in unison on the Broughton suspension bridge, the immense vibration caused by the combined strides of all the soldiers was accidentally the same as that of the bridge's resonant frequency. This led to the destruction of the bridge, but thankfully there were no fatalities.

## Damping

Damping is any phenomenon that affects and reduces the stored energy in the oscillation in an oscillatory system. Since most systems display oscillatory behaviour when disrupted from equilibrium, there are different types of damping. The damping ratio can be defined as a measure of the degree of loss in oscillations after a disturbance and does not have a dimension or unit.

## Q Factor

Known as the Quality factor, it is a dimensionless measure of the degree to how underdamped a system is. Quality Factor is the ratio of the total energy stored in the resonator to the energy lost in one radian of the cycle. A higher Q factor value signifies a lower rate of energy loss, so a high Q value is desirable.

## Applications of Resonance

• A tank circuit, which is a parallel connection of a capacitor and an inductor, meant to serve as a resonator, is used to stabilize the electrical frequency of an AC oscillator circuit.
• Resonant circuits can be used to restrict a particular frequency or a range of frequencies, acting as a frequency filter.