Introduction

What This Section Sets Up

• A mechanical wave is a disturbance produced in an elastic medium by periodic vibrations of the particles of the medium about their mean positions. Energy and momentum pass from particle to particle, so a wave transfers energy from one point to another without transferring matter.
• Electromagnetic waves need no material medium and are therefore non-mechanical waves. Sound, water waves and waves on a string are mechanical.
• Nothing in this section is examined on its own. It exists to name what the chapter will cover: reflection of mechanical waves, the principle of superposition, and the phenomena that follow from it — stationary waves and beats — together with their applications.