Radar stations are strong sources of non-ionizing radiation.
Non-Ionizing radiation is a form of electromagnetic radiation having less energy than ultraviolet (UV) light or X-rays. While this makes non-ionizing radiation safer than the ionizing kind, it still carries some risks. As with all forms of radiation, you protect yourself by shielding against it and managing distance between yourself and its source. Various government and independent organizations have defined safe levels of exposure, and equipment manufacturers follow those guidelines.
Properties
As radiation's energy increases with decreasing wavelength, non-ionizing radiation has relatively long wavelengths, spanning visible light of about 450 nanometers all the way to radio waves of several meters. Other than light, non-ionizing radiation is invisible, though easily detected with electronic devices. It travels in straight lines and can be guided or absorbed by various materials.
Heating
Unlike ionizing radiation, which can directly damage biological tissue, non-ionizing radiation simply heats things up. Polar molecules, such as water, absorb the radiation's energy, becoming warm. Microwave ovens and heat lamps are common examples of this, though it happens with all wavelengths to some degree. Excessive heat can cause pain and tissue damage.
Exposure
The Food and Drug Administration (FDA) has set limits for exposure to radio waves in MRI machines, though most of the same ideas apply to other sources of non-ionizing radiation. Exposure has been defined in terms of specific absorption rate (SAR), which describes how many watts of energy become absorbed by a kilogram of human tissue. The FDA's safe exposure limits are no more than 8 watts per kilogram of tissue for five minutes, or 4 watts/kilogram for 15 minutes. Other organizations, such as the Federal Communications Commission (FCC) and the Occupational Safety and Heath Administration (OSHA), set exposure limits for specific workplace settings and types of equipment.
Shielding
You can prevent non-ionizing radiation from leaking out of equipment and cabling by using various kinds of shielding. In many instances, equipment designers use grounded metal cages to block radio-frequency energy. The energy can perform its intended function inside the cage but cannot escape it. A common example of shielding is coaxial cable. It consists of an inner wire conductor surrounded by a plastic jacket, in turn surrounded by a conducting mesh. The outer mesh keeps radio-frequency radiation from escaping the cable, especially when it's connected to an electrical ground.
Distance
All radiation from a point-like source diminishes in intensity as the reciprocal of the square of the distance from the source. Scientists and engineers call this the inverse-square law. With increasing distance, non-ionizing radiation's power drops off to a tiny fraction of what it is nearby. This fact, along with the effects of shielding, allow people to work safely with radiation-producing equipment.
Tags: non-ionizing radiation, radiation from, exposure limits, radiation energy, radio waves, sources non-ionizing
