# 1: Harmonic Oscillation

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Oscillators are the basic building blocks of waves. We begin by discussing the harmonic oscillator. We will identify the general principles that make the harmonic oscillator so special and important. To make use of these principles, we must introduce the mathematical device of complex numbers. But the advantage of introducing this mathematics is that we can understand the solution to the harmonic oscillator problem in a new way. We show that the properties of linearity and time translation invariance lead to solutions that are complex exponential functions of time.

Preview

In this chapter, we discuss harmonic oscillation in systems with only one degree of freedom.

1. We begin with a review of the simple harmonic oscillator, noting that the equation of motion of a free oscillator is linear and invariant under time translation;
2. We discuss linearity in more detail, arguing that it is the generic situation for small oscillations about a point of stable equilibrium;
3. We discuss time translation invariance of the harmonic oscillator, and the connection between harmonic oscillation and uniform circular motion;
4. We introduce complex numbers, and discuss their arithmetic;
5. Using complex numbers, we find solutions to the equation of motion for the harmonic oscillator that behave as simply as possible under time translations. We call these solutions “irreducible.” We show that they are actually complex exponentials.
6. We discuss an $$LC$$ circuit and draw an analogy between it and a system of a mass and springs.
7. We discuss units.
8. We give one simple example of a nonlinear oscillator.

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