The book explores electromagnetic (EM) waves, which are present everywhere--from radio, television, and cell phones to satellite dishes, antennas, and WiFi. The propagation of EM waves is governed by Maxwell's equations. When these waves pass through a medium, they slow down and refract, while in a metallic medium, they are reflected. Metallic boxes and pipes can store and direct EM waves, known as cavities and waveguides. Oscillating currents generate and transmit EM waves through antennas, allowing for long-distance communication after the waves propagate. Since oscillating currents emit EM waves, the author uses coaxial cables and transmission lines to reduce radiation and carry high-frequency currents efficiently. EM waves at very high frequencies in the optical range are responsible for transmitting visual information. The author also discusses lenses and optical instruments like telescopes and microscopes, which are used to magnify optical signals.

Additionally, the quantum mechanical origins of a material's permittivity, which affects the speed of light through the medium, are examined.