Introduction

A wave is a periodic disturbance–a back-and-forth change of some kind that is repeated regularly as time goes on–that spreads out from a source and carries energy with it. Throw a stone into a lake: water waves move out from the splash. Clap your hands: sound waves carry the noise around you. Switch on a lamp: light waves flood the room. Water waves, sound waves, and light waves are very different from one another in various ways, but all have in common some basic properties that are explored in this chapter.