Waves: Transverse, Longitudinal and Their Characteristics

<h3>What is a wave?</h3><p>A <strong>wave</strong> is a disturbance that transfers <strong>energy</strong> from one point to another without transferring matter. Waves that need a material to travel through, like water and sound, are called <strong>mechanical waves</strong>.</p><h3>Two types of waves</h3><ul><li><strong>Transverse wave:</strong> particles vibrate at right angles to the direction of travel. Example: ripples on a pond.</li><li><strong>Longitudinal wave:</strong> particles vibrate along the same direction the wave travels, forming compressions and rarefactions. Example: sound in air.</li></ul><h3>Characteristics of a wave</h3><ul><li><strong>Wavelength (&lambda;):</strong> distance between two successive identical points, in metres.</li><li><strong>Frequency (f):</strong> number of complete waves per second, in hertz (Hz).</li><li><strong>Amplitude:</strong> maximum displacement from the rest position.</li><li><strong>Period (T):</strong> time for one complete wave; <code>f = 1 / T</code>.</li></ul><p>The <strong>wave equation</strong> links speed, frequency and wavelength:</p><p><code>Speed = Frequency &times; Wavelength</code> (v = f&lambda;)</p><div class="callout"><strong>Kenyan context:</strong> When you tune a radio to Citizen or KBC, you are selecting a particular frequency of electromagnetic wave. Mobile phone signals on Safaricom and Airtel networks are also waves &mdash; the same physics carries an M-Pesa confirmation message to your phone in an instant.</div>