Microwaves are a form of electromagnetic radiation with wavelengths ranging from one meter to one millimeter; with frequencies between 300 MHz (100 cm) and 300 GHz (0.1 cm). The prefix micro- in microwave is not meant to suggest a wavelength in the micrometer range. It indicates that microwaves are "small", compared to the radio waves used prior to microwave technology, in that they have shorter wavelengths. The boundaries between far infrared, terahertz radiation, microwaves, and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study.
Microwaves travel by line-of-sight; unlike lower frequency radio waves they do not diffract around hills, follow the earth's surface as ground waves, or reflect from the ionosphere, so terrestrial microwave communication links are limited by the visual horizon to about 40 miles (64 km). At the high end of the band they are absorbed by gases in the atmosphere, limiting practical communication distances to around a kilometer.
Microwaves are extremely widely used in modern technology. They are used for point-to-point communication links, wireless networks, microwave radio relay networks, radar, satellite and spacecraft communication, medical diathermy and cancer treatment, remote sensing, radio astronomy, particle accelerators, spectroscopy, industrial heating, collision avoidance systems, garage door openers and keyless entry systems, and for cooking food in microwave ovens.
According to a recent study, Microwave use across the European Union (EU) emits as much carbon dioxide as nearly 7 million cars.
The factors under investigation were: climate change, depletion of natural resources and ecological toxicity. As per the study, the main environmental “hotspots” are materials used to manufacture microwaves, the manufacturing process and end-of-life waste management.
It found that, on average, one microwave uses 573 kilowatt hour (kWh) of electricity over its lifetime of eight years which is equivalent to the electricity consumed by a 7-watt LED light bulb, switched on continuously for almost nine years.
Efforts to reduce consumption should focus on improving consumer awareness and behaviour to use appliances more efficiently. Electricity consumption by microwaves can be reduced by adjusting the time of cooking to the type of food.
Waste is another major problem because due to their relative low cost and ease of manufacture, consumers are throwing more electrical and electronic (EE) equipment away than ever before, including microwaves.