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# Phase (waves)

Phase is the position of a point in time (an instant) on a waveform cycle. 

## Absolute phase

Absolute phase refers to the phase of a waveform relative to some standard (strictly speaking, phase is always relative).

## Amplitude

The amplitude of a periodic variable is a measure of its change over a single period (such as time or spatial period).

## Coherence (physics)

In physics, two wave sources are perfectly coherent if they have a constant phase difference and the same frequency, and the same waveform.

## Degree (angle)

A degree (in full, a degree of arc, arc degree, or arcdegree), usually denoted by ° (the degree symbol), is a measurement of a plane angle, defined so that a full rotation is 360 degrees.

## Displacement (vector)

A displacement is a vector whose length is the shortest distance from the initial to the final position of a point P. It quantifies both the distance and direction of an imaginary motion along a straight line from the initial position to the final position of the point.

## Frequency

Frequency is the number of occurrences of a repeating event per unit of time.

## Harmonic

A harmonic is any member of the harmonic series, a divergent infinite series.

In electrical engineering, a sinusoid with angle modulation can be decomposed into, or synthesized from, two amplitude-modulated sinusoids that are offset in phase by one-quarter cycle (/2 radians).

## Indiana University

Indiana University (IU) is a multi-campus public university system in the state of Indiana, United States.

## Instantaneous phase

Instantaneous phase and instantaneous frequency are important concepts in signal processing that occur in the context of the representation and analysis of time-varying functions.

## Lissajous curve

In mathematics, a Lissajous curve, also known as Lissajous figure or Bowditch curve, is the graph of a system of parametric equations which describe complex harmonic motion.

## National Institute of Standards and Technology

The National Institute of Standards and Technology (NIST) is one of the oldest physical science laboratories in the United States.

## Origin (mathematics)

In mathematics, the origin of a Euclidean space is a special point, usually denoted by the letter O, used as a fixed point of reference for the geometry of the surrounding space.

## Oscilloscope

An oscilloscope, previously called an oscillograph, and informally known as a scope or o-scope, CRO (for cathode-ray oscilloscope), or DSO (for the more modern digital storage oscilloscope), is a type of electronic test instrument that allows observation of varying signal voltages, usually as a two-dimensional plot of one or more signals as a function of time.

## Phase angle

In the context of phasors, phase angle refers to the angular component of the complex number representation of the function.

## Phase problem

In physics, the phase problem is the problem of loss of information concerning the phase that can occur when making a physical measurement.

## Phase velocity

The phase velocity of a wave is the rate at which the phase of the wave propagates in space.

## Phasor

In physics and engineering, a phasor (a portmanteau of phase vector), is a complex number representing a sinusoidal function whose amplitude (A), angular frequency (ω), and initial phase (θ) are time-invariant.

## Plane wave

In the physics of wave propagation, a plane wave (also spelled planewave) is a wave whose wavefronts (surfaces of constant phase) are infinite parallel planes.

## Polarization (waves)

Polarization (also polarisation) is a property applying to transverse waves that specifies the geometrical orientation of the oscillations.

## Principal value

In complex analysis, the principal values of a multivalued function are the values along one chosen branch of that function, so that it is single-valued.

The radian (SI symbol rad) is the SI unit for measuring angles, and is the standard unit of angular measure used in many areas of mathematics.

## Simple harmonic motion

In mechanics and physics, simple harmonic motion is a special type of periodic motion or oscillation motion where the restoring force is directly proportional to the displacement and acts in the direction opposite to that of displacement.

## Sine wave

A sine wave or sinusoid is a mathematical curve that describes a smooth periodic oscillation.

## Spectrogram

A spectrogram is a visual representation of the spectrum of frequencies of sound or other signal as they vary with time.

## Turn (geometry)

A turn is a unit of plane angle measurement equal to 2pi radians, 360 degrees or 400 gradians.

## Wave

In physics, a wave is a disturbance that transfers energy through matter or space, with little or no associated mass transport.

## Wave interference

In physics, interference is a phenomenon in which two waves superpose to form a resultant wave of greater, lower, or the same amplitude.

## Waveform

A waveform is the shape and form of a signal such as a wave moving in a physical medium or an abstract representation.

## References

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