An electromagnetic wave can be considered as a progressive transverse wave that consists of a fluctuating electric field coupled with a fluctuating magnetic field at right angles to it, as shown in Figure 13.1. Don’t worry if this seems a difficult idea at this stage; it will become clearer when we discuss electric and magnetic fields in later topics. For the moment the important thing to remember is that, unlike mechanical waves, electromagnetic waves do not necessarily require a medium for their propagation. They travel through empty space (vacuum) at a speed of very nearly 3 × 108 m s−1, commonly called the speed of light (symbol c), and their frequency can be obtained from their wavelength via Equation (12.1) (v = fλ). The speed of light in air is very slightly less than in vacuum but considerably less in some other materials, as we shall see later.
KeywordsElectromagnetic Wave Critical Angle Total Internal Reflection Path Difference Monochromatic Light
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