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3.5 Visualisation of a Wave Using SciLab 21its argument by 2π (the Greek symbol “pi”), where π is about 3.1415. Accordingly,we can express a wave travelling in the x-direction as:[ ( xA(x, t) = A o sin 2πλ − t )]T(3.2)where A is a property experiencing oscillations such as sea level, A o is the constantwave amplitude, being half the difference between maximum and minimum valuesof A, λ is wavelength, and T is wave period. This wave displays sinusoidal variationsboth in time and space. Equation (3.2) describes a wave void of variation in they direction. Accordingly, wavefronts (crests and troughs) are parallel to each other.A wave like this is called a plane wave.3.5 Visualisation of a Wave Using SciLab3.5.1 A Simple Wave Made of Vertically Moving BarsIn order to visualise a wave, we consider a number of vertical bars sitting in a rownext to each other. Bars rise or sink in a systematic pattern. The firs bar gives therhythm by moving up and down in a sinusoidal fashion. Any neighboring bar doesthe same but slightly delayed in time. Whenever a bar is above a certain horizon, itturns blue. When it is below this horizon, it turns red.Figure 3.3 shows a snapshot of this wave. There is no lateral motion of any of thebars, but the pattern seems to move toward the right. The speed at which the patternmoves is called phase speed of a wave.3.5.2 Sample ScriptThe SciLab script for this wave demonstration, called “WaveSim.sce”, can be foundin the folder “Miscellaneous” on the CD-ROM of this book. Before using this script,however, the reader should read the following brief introduction to SciLab scripting.Fig. 3.3 Snapshot of organised wave motions by bars