- amplitude
- the maximum displacement from the equilibrium position of an object oscillating around the equilibrium position

- antinode
- the location of maximum amplitude in standing waves

- beat frequency
- the frequency of the amplitude fluctuations of a wave

- constructive interference
- when two waves arrive at the same point exactly in phase; that is, the crests of the two waves are precisely aligned, as are the troughs

- critical damping
- the condition in which the damping of an oscillator causes it to return as quickly as possible to its equilibrium position without oscillating back and forth about this position

- deformation
- displacement from equilibrium

- destructive interference
- when two identical waves arrive at the same point exactly out of phase; that is, precisely aligned crest to trough

- elastic potential energy
- potential energy stored as a result of deformation of an elastic object, such as the stretching of a spring

- force constant
- a constant related to the rigidity of a system: the larger the force constant, the more rigid the system; the force constant is represented by
*k*

- frequency
- number of events per unit of time

- fundamental frequency
- the lowest frequency of a periodic waveform

- intensity
- power per unit area

- longitudinal wave
- a wave in which the disturbance is parallel to the direction of propagation

- natural frequency
- the frequency at which a system would oscillate if there were no driving and no damping forces

- nodes
- the points where the string does not move; more generally, nodes are where the wave disturbance is zero in a standing wave

- oscillate
- moving back and forth regularly between two points

- over damping
- the condition in which damping of an oscillator causes it to return to equilibrium without oscillating; oscillator moves more slowly toward equilibrium than in the critically damped system

- overtones
- multiples of the fundamental frequency of a sound

- period
- time it takes to complete one oscillation

- periodic motion
- motion that repeats itself at regular time intervals

- resonance
- the phenomenon of driving a system with a frequency equal to the system's natural frequency

- resonate
- a system being driven at its natural frequency

- restoring force
- force acting in opposition to the force caused by a deformation

- simple harmonic motion
- the oscillatory motion in a system where the net force can be described by Hooke’s law

- simple harmonic oscillator
- a device that implements Hooke’s law, such as a mass that is attached to a spring, with the other end of the spring being connected to a rigid support such as a wall

- simple pendulum
- an object with a small mass suspended from a light wire or string

- superposition
- the phenomenon that occurs when two or more waves arrive at the same point

- transverse wave
- a wave in which the disturbance is perpendicular to the direction of propagation

- under damping
- the condition in which damping of an oscillator causes it to return to equilibrium with the amplitude gradually decreasing to zero; system returns to equilibrium faster but overshoots and crosses the equilibrium position one or more times

- wave
- a disturbance that moves from its source and carries energy

- wave velocity
- the speed at which the disturbance moves. Also called the propagation velocity or propagation speed

- wavelength
- the distance between adjacent identical parts of a wave