Phase (waves)

Phase specifies a periodic waveform’s position within its cycle relative to a reference, commonly expressed as an angle or fraction of a period.

Phase difference: The angular or temporal separation between corresponding points in two periodic signals. It quantifies the relative cycle positions that define interference and synchronization.
Periodic function: A function that repeats its values at regular intervals. A repeating waveform provides the cycle whose position phase describes.
Lock-in amplifier: An instrument that extracts a weak periodic signal by comparing it with a reference oscillator. Its reference comparison measures signal amplitude and phase despite noise.
Amplitude: The maximum magnitude of a periodic quantity’s displacement from its equilibrium value. Amplitude sets waveform size, whereas phase sets its position within the cycle.
Phase shift: A displacement of a waveform’s phase relative to a reference signal or its original position. A phase change moves the waveform’s position within its cycle.
Period (physics): The time required for a periodic process to complete one cycle. Phase can be expressed as elapsed time divided by this cycle duration.
Phase-locked loop: A feedback system that adjusts an oscillator to maintain a chosen phase relation with an input signal. It uses phase error to synchronize oscillators and recover timing.
Wavelength: The spatial distance over which a wave’s pattern repeats once. Wavelength measures spatial cycle length; phase identifies position within that cycle.
Phase angle: An angular measure of position within a periodic cycle, usually given in radians or degrees. It expresses phase numerically, with one complete cycle equal to 2π radians.
Frequency: The number of cycles of a repeating event occurring per unit time. Frequency sets how quickly phase advances in a time-varying signal.

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