Oscillation

Oscillation refers to the repetitive variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. The term vibration is precisely used to describe mechanical oscillation. Familiar examples of oscillation include a swinging pendulum and alternating current.

Oscillations occur not only in mechanical systems but also in dynamic systems in virtually every area of science: for example the beating of the human heart (for circulation), business cycles in economics, predator–prey population cycles in ecology, geothermal geysers in geology, vibrating strings in musical instruments, periodic firing of nerve cells in the brain, and the periodic swelling of Cepheid variable stars in astronomy.

Types of Oscillation

Oscillations can be categorized in various ways, but are often described by the behaviour over time, the cause or the environment in which they occur.

Free oscillation

A system can be set into oscillatory motion by an initial disturbance. This is typically a displacement of the system from its equilibrium position, followed by release. The system will then continue to oscillate freely. If there is no damping, it will continue at a constant amplitude forever.

Forced oscillation

A system may be driven by an external force. In this case, the oscillations are said to be driven. The external force is periodic and at a particular frequency. The frequency is known as the driving frequency.

Damped oscillation

In real-world systems, the second law of thermodynamics dictates that there is always some damping. Although this may be small, it eventually becomes dominant and causes the oscillation to die away.

Mathematical description

The simplest mathematical description of an oscillation can be found by considering a pendulum. Using Newton's second law and assuming small angle oscillations, we can derive the equation of motion as a simple harmonic oscillator.

See also

• Harmonic oscillator
• Damping
• Resonance
• Vibration
• Wave