ABSTRACT
What is light? This question had been asked from the very beginning of human civilization. Particle? Wave? Perhaps, this is one of the longest debated scientific topics in human history. In this chapter, we review the Maxwell continuum electromagnetic wave theory of light. Starting from Maxwell's equations, we derive the electromagnetic (EM) wave equation and obtain its plane-wave solution; we then introduce the classical superposition “principle” and the wavepacket concept of the electromagnetic field, which is a mathematical result of the Fourier transform. The electromagnetic field of light is never easy to measure directly. Most of the observations of light are based on the measurement of its energy flow or intensity. The measurement of light is another focus of this chapter.
