What is electromagnetic radiation (EMR); the electromagnetic spectrum; electromagnetic fields (EMFs)?
(Excerpts and illustrations from Electromagnetic Fields: A Consumer’s Guide to the Issues and How to Protect Ourselves by B. Blake Levitt, Harcourt Brace, 1995. Used by permission of author.)*All links below will open in a new browser window. All documents on this page are PDF files.
Electromagnetic radiation is the term used to describe electromagnetic energy radiating away from its source. It is expressed in wavelengths calculated along what is called the electromagnetic spectrum. There are many wavelength magnitudes along the spectrum, which includes everything from the earth’s own natural pulsations, to electric power, to visible light, to cosmic events.
The electromagnetic spectrum is divided into ionizing and nonionizing radiation. Ionizing radiation consists of very short wavelengths (like X-rays), which have enough power to knock electrons off their nuclear orbits and therefore can cause permanent damage at the cellular level, such as cancer or genetic mutations. Nonionizing radiation consists of longer wavelengths with generally less power and is considered incapable of knocking electrons off their orbit around the nucleus. Energy is directly related to the inverse of wavelength. The longer the wave, the less energy it creates; the shorter the wave, the more energy it can create.
Although less powerful, nonionizing radiation is capable of causing a host of biological effects, so it is far from harmless.
The dividing line between ionizing and nonionizing radiation is around visible light. The problem is that visible light covers a wide portion of the spectrum. (Each color, for instance, is a different wavelength.) So no on can say precisely where one form of radiation leaves off and the other begins, but it is thought to be in the lower ultraviolet ranges, or possibly below.
Electromagnetic field is the term used to describe electric and magnetic fields. In general, a field is defined as a space in which energy exists. Actually as field is a concept used to describe the influence of something on its surrounding area.
Electric fields exist whenever electric charges are present, that is, whenever electricity or electrical equipment is in use. A magnetic field is produced whenever there is electrical current flowing in a conductor or wire. All magnetic fields run perpendicular to electrical current. In other words, while electric current runs in straight lines, magnetic fields surround the line in circular fashion. When the electricity is turned off, there is no magnetic field, although an electric field will still exist to some extent in any wire or conductor.
All electromagnetic fields are expressed in wavelengths and move outward at the speed of light – approximately 186,00 miles per second.
Both electric and magnetic fields decrease rapidly with distance from the source.
Some common consumer products have complex electromagnetic fields. A television screen or the cathode-ray tube on a computer monitor, for instance, plugs into a wall outlet, thereby using electricity in the 50-60 Hz area, then utilizes a broad band of wavelengths that extend all the way up through the visible-light spectrum. At the top ends of the screen’s field, the ionizing band may well be crossed into.