Radiation is all around us, every moment of every day. While this idea may be intimidating at first, there's very little to worry about. Most forms of radiation pose absolutely no health risks. In fact, some forms, like light energy, are essential to life on Earth, while others, including radio waves and microwaves, simply make life more convenient for people who have access to them.

Few of us ever consider the similarity of light and radio waves, nor do we think of them in terms of radiation. In fact, visible light and radio waves make up part of a large category of radiation that physicists call electromagnetic waves.

Electromagnetic waves and sound or ocean waves have more in common than it might seem at first. Waves of all types are produced by vibration. When a musician plucks a guitar string, for example, its back-and-forth motion produces high- and low-pressure waves in the surrounding air. Similarly, electromagnetic waves are produced by vibrating electric charges that give off tiny packets of energy called photons. But unlike ocean or sound waves, electromagnetic waves transfer energy through electric and magnetic fields, not through matter (water or air).

All types of electromagnetic waves transfer energy in this way and together constitute what physicists call the electromagnetic spectrum. What distinguishes one wave on the spectrum from another is the amount of energy each wave carries -- specifically, the level of energy in the photons of each.

This energy level determines the wavelength and frequency of a given wave: The more energy each photon carries, the shorter the wavelength and the higher the frequency of the wave. Along the spectrum, electromagnetic waves are categorized according to their wavelengths and frequencies, with radio waves occupying the low-frequency end, gamma waves at the high-frequency end, and visible light in the middle.