## Tuesday, May 14, 2019

### Electromagnetic Energy: Introduction

Energy can appear within creation in several forms, and one of those forms is electromagnetic energy. This is a huge topic of physics, and it will be introduced by taking a look at light.

Electromagnetic energy (EM) is a category of energy forms that propagates1 through space at the speed of light, c, which is 3 X 108 m/s or 186,000 mph. Electromagnetic energy is categorized by it's wavelength and frequency. Certain form of EM are defined by ranges of wavelength and frequency.

Because EM travels at the speed of light, wavelength, λ, and frequency, f, are reciprocals and conform to the wave equation:

v = fλ

Since v is always the speed of light for all EM forms, as f goes up, λ goes down.

Ranges of frequencies (and thus wavelengths) determine the type of EM in question. Certain ranges are called radio waves (AM and FM have different frequency ranges—take a look at your car radio tuner, perhaps). Other familiar ranges include radar, x-ray, and microwave ovens.

Electromagnetic energy behaves differently in different situation. In many cases, it behaves like a wave that will reflect (bounce off of) from surfaces or refract (bend around) edges or objects. However, in other cases, it behaves like a particle. Thus, EM energy is thought to have both properties that are explained by both wave and particle models. In reality, the complexities of EM energy are not fully explained by either model, but each model is useful for gaining understanding of different principles of EM energy.

1 "propagates" is used to describe the motion of waves through a medium. Mechanical waves (such as sound) propagate by transferring energy through collision of molecules. Electromagnetic waves propagate differently and do not rely on matter as a medium. Once upon a time, scientists theorized that the universe was filled with something they called the aether that was responsible for the propagation of electromagnetic waves.