# What Is Amplitude

The amplitude a of a wave is the magnitude of the maximum displacement of the elements from their equilibrium positions as the wave passes through them. Since a is a magnitude, it is a positive quantity, even if the displacement is negative. The example for this is the sound waves, which are oscillations in air and its amplitude is proportional to the change in pressure during one oscillation. In case of regular oscillations, the graph if drawn shows the variables as the vertical axis and the time as the horizontal axis. The amplitude here is the distance between the extreme of the curve and the equilibrium position.

The phase of the wave is the argument (kx – ωt+φ) of the oscillatory terms in (kx – ωt+φ). It describes the state of motion as the wave sweeps through a string element at a particular position x. It changes linearly with time t. The sine function also changes with time, oscillating between +1 and –1. Its extreme positive value +1 corresponds to a peak of the wave moving through the element; then the value of y at position x is a. Its extreme negative value –1 corresponds to a valley of the wave moving through the element, then the value of y at position x is  –a. Thus, the sine function and the time dependent phase of a wave correspond to the oscillation of a string element, and the amplitude of the wave determines the extremes of the element’s displacement. The constant φ is called the initial phase angle. The value of φ is determined by the initial (t=0) displacement and velocity of th eelement (say, at x=0). It is always possible to choose origin (x=0) and the initial instant (t=0) such that φ=0. There is no loss of generality in working with φ=0. Amplitude is measured in the amount of force applied over an area and the unit of measurement in case of acoustics is newton per squaremeter (N/m2), where one newton is the force amount used to accelerate 1kg of object by 1 meter in one second. Intensity of sound is directly proportional to the amplitude. Wavelength of the light tells about the type of light where as amplitude of light tells about the intensity of light. There are different types of amplitudes like 1) peak to peak amplitude, 2) peak amplitude, 3) Semi –amplitude, 4) root mean square amplitude and, 5) pulse amplitude. These different types of amplitude are used in different fields like peak to peak amplitude in audio system measurement, telecommunication, RMS in electrical engineering, pulse amplitude in telecommunication etc.