Terminology

s = Displacement (unit = metre, m): Displacement is the position of a particle of the medium relative to its equilibrium position.

T = Period (unit = second, s): Period is the time for one complete cycle or oscillation of the medium.

φ = Phase (unit = degrees or radians): Phase is the position (with respect to time) of the oscillation taking zero disturbance as zero time. As the disturbance goes through a cycle the position in the cycle is called the phase and, since the mathematical expression for the disturbance usually involves a sine function of the time, the phase is measured in degrees or radians. A full cycle is 360° and a quarter of a cycle is 90°.

A or a = Amplitude (unit = various): Amplitude is the maximum disturbance of the medium from its equilibrium position or state.

f = Frequency (unit = hertz, Hz): Frequency is the number of waves passing any point per second or the number of oscillations of the medium per second.

λ = Wavelength (unit = metre, m): Wavelength is the distance between two points on successive wave fronts that are in phase. A Wave Front is a line joining all points that are in phase. Successive wave fronts are drawn at the same phase and waves are one wavelength apart. Waves travel perpendicular to the wave front.

I = Intensity (unit = W/m² = kg/s³, W·m⁻² = kg·s⁻³): Intensity is the energy passing through unit area (perpendicular to the area) per second.

v = Speed (unit = m/s, m·s⁻¹): Speed is the distance travelled by a wave front per second.