Introduction

This chapter describes those properties of electromagnetic radiation (EMR) relevant to remote sensing. Specifically, Section 3.2 gives a brief description of the nature of electromagnetic radiation, its propagation in different media and its polarization. Section 3.3 describes several different ways of describing radiation fluxes. Section 3.4 discusses blackbody radiation, Planck's equation and the concepts of emission and absorption. Section 3.5 discusses the basic optics applicable to an instrument operating in the visible and infrared, then describes the operation and spatial resolution of an ideal instrument. The section concludes with a discussion of terms such as bandwidth and signal-to-noise ratio that are applicable to real instruments.

Descriptions of electromagnetic radiation

As many textbooks describe, EMR has a dual nature, in that it behaves both as discrete quanta of radiation and as electromagnetic waves (Jackson, 1975; Born and Wolf, 1999). In the quantum description, radiation propagates as photons, which are massless, discrete bundles of energy released by atomic or molecular changes of state.