115 Introduction to Oscillatory Motion and Waves

What do an ocean buoy, a child on a swing, the cone of a speaker, a guitar string, atoms in a crystal, the motion of the chest during breathing, and the beating of a heart all have in common? They all oscillate—that is, they move back and forth between two points. Oscillations are found throughout nature and biology, and they share common underlying features. All oscillatory motion involves force and energy. For instance, pushing a child on a swing or plucking a guitar string transfers energy to the system, initiating its motion. Even molecular vibrations in tissues or organs can be understood in terms of oscillatory energy.

Some oscillations give rise to waves. For example, a plucked guitar string produces sound waves. You can create water waves by slapping the surface of a pool. Some waves, such as light or seismic waves, may be invisible but still carry energy. In fact, all waves are disturbances that travel from a source and transmit energy. In the context of life sciences, waves play crucial roles—from sound waves used in communication, to electromagnetic waves in imaging, to pressure waves in cardiovascular dynamics.

In this chapter, we explore oscillatory motion and wave behavior. You’ll learn that just a few fundamental principles describe a wide range of wave phenomena. We begin by examining the basic forces behind oscillations, especially the restoring force that causes systems to return to equilibrium. Then, we delve into types of oscillatory motion such as simple harmonic motion and damped motion. Finally, we investigate what happens when multiple waves interact in the same space—a concept known as superposition and interference, which has important applications in acoustics, medical diagnostics, and wave-based imaging.