BBC-The electromagnetic spectrum
The electromagnetic spectrum activity
Infrared, x-rays, visible light... where do they all fit in the electromagnetic spectrum? Find out in this activity.
What is electromagnetic energy?
Electromagnetic energy consists of waves of electric and magnetic energy radiating through space, and travelling at the speed of light. The area where these waves are found is called an electromagnetic field. The main source of electromagnetic energy is the sun, but man-made sources account for large amounts of the electromagnetic radiation in our day-to-day environment. Items such as hairdryers, electrical ovens, fluorescent lights, microwave ovens, stereos, wireless phones and computers produce electromagnetic fields of varying intensities.
2. How is electromagnetic energy measured?
Electromagnetic energy is measured in units of wavelength and frequency. The wavelength is the distance that a wave travels in one cycle and is measured in metres. The frequency is measured by the number of cycles per second and the unit of measurement is the Hertz (Hz). One cycle per second equals one Hertz. One kilohertz (kHz) is 1,000 Hz; one megahertz (MHz) is one million Hz; one gigahertz is one billion Hz. The frequency of a wave is inversely related to its length - at 50 Hz the wavelengths are 6,000 Km, and at 100 MHz they are 3 metres. Electromagnetic fields are arranged according to their frequencies in an orderly fashion in what is known as the electromagnetic spectrum.
3. What is radiofrequency radiation?
Radiofrequency (RF) fields are part of the electromagnetic (EM) spectrum. The EM spectrum is divided into ionizing and non-ionizing bands based on how the wave interacts with biological tissue.
The non-ionizing portion, usually in the frequency range up to 300 GHz, doesn't affect biological tissue and includes the extremely low frequency (ELF) band, radio waves and microwaves in the radiofrequency communication band, and infrared and visible light. The RF part of the spectrum is usually defined as being between 30 kHz and 300 GHz. RF radiation is mainly used in telecommunications. Mobile phones employ frequencies in the range of 800 MHz to 2GHz. Other uses of RF energy include microwave ovens and medical treatments.
The ionizing portion of the EM spectrum (made up of ultraviolet light, gamma rays and X-rays that have very short wavelengths, very high frequencies, and very high intensities) does affect biological tissue. Mobile phones do not operate in this spectrum. For more on this, see "Primer".
More questions and answers
The Parliamentary Assembly, Council of Europe
Doc. 12608 . 6 May 2011
The potential dangers of electromagnetic fields and their effect on the environment
Committee on the Environment, Agriculture and Local and Regional Affairs
Rapporteur: Mr Jean HUSS, Luxembourg, Socialist Group
Challenge of Exotic Weapons / Foriegn Affairs / Canada
Foreign Affairs and International Trade Canada
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Toronto / Ontario / Canada
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