Vibrations

Abstract

Vibration, a change of the state of a system periodic in time (oscillator) and occurring when

• a system is displaced from its mechanical, electrical or thermal equilibrium by an external perturbation, and

• forces arise that drive the system back towards equilibrium. Vibrations occur in almost all physical systems.

Wave (see p. 287), change of the state of a system periodic in space and time and occurring when

• a system consists of subsystems that all are oscillatory,

• the subsystems may interact with each other, hence, energy may be transferred from one subsystem to another neighboring subsystem, and

• at least one of the subsystems is driven from its mechanical, electrical or thermal equilibrium by an external perturbation.

Energy is transfered from one subsystem to other subsystems without any mass transport being involved.

■ Sound consists of density waves which occur in media. Light consists of electromagnetic waves within a certain frequency interval.