Propagation of Energy by Electromagnetic Waves

Abstract

If a stone is thrown, travels, and hits a target, the damage caused is readily attributed to the energy of the stone. That the moving stone is a carrier of energy is easily understood. It is less easy to understand how the energy coming from a radio transmitter is sensed by a radio receiver. The propagation of energy, in this case, is through electromagnetic waves that are invisible. The heat we feel when we place our hand near a hot oven is due to the infrared waves from the oven, which are also electromagnetic waves. The visible light from an electric lamp also consists of electromagnetic waves. In this chapter, wediscuss electromagnetic waves and what causes the difference among radio waves, infrared waves, visible light, and any other manifestation of these waves. After presenting the classical description based on wave theory that applies to their macroscopic behavior, we briefly introduce the quantum-mechanical concepts that operate on atomic and microscopic scales, as needed for the purposes of this book.