Introduction

Summary

Whenever we see or hear anything, we do so because of the existence of waves. Electromagnetic waves cover a spectrum from low frequency radio waves, through visible light to X- and gamma rays. Sound propagates as a wave through the air. When someone sings or plays a musical instrument, the standing waves in their vocal chords, guitar strings or drumskins produce a pressure change, or sound wave, which is audible. Although these examples alone would be sufficient to motivate their study, wave phenomena occur in many other physical systems. Waves can propagate both on the surface of solid bodies (for example, as earthquakes) and through the bulk of a solid (for example, in seismic oil prospecting). The surface of the sea is perhaps the most obvious example of a wave bearing medium. Water waves vary in size from the small ripples caused by raindrops, through shock waves such as the Severn bore, to enormous ocean waves that can capsize large ships. Waves in different media can interact, often with devastating effects, for example when an underwater earthquake causes a tsunami, a huge wall of water that can destroy coastal settlements, or when the waves generated by the wind blowing on a bridge produce a catastrophic resonance.

Wave phenomena emerge in unexpected contexts. The flow of traffic along a road can support a variety of wave-like disturbances as anybody who has sat in slowly moving traffic will know.