Infrared [infrared radiation: Electromagnetic radiation emitted from a hot object. ] light, microwavesmicrowaves: Electromagnetic radiation with a frequency between that of visible light and radio waves. and radio wavesradio waves: Low frequency electromagnetic radiation used to transmit information such as television and radio programmes. are all used to transmit information such as computer data, telephone calls and TV signals.
Information such as computer data and telephone calls can be converted into infrared signals and transmitted by optical fibres. Optical fibres are able to carry more information than an ordinary cable of the same thickness. In addition the signals they carry do not weaken so much over long distances. Television remote controls use infrared light to transmit coded signals to the television set in order to, for example, change channels or adjust the volume.
Microwave radiation can be used to transmit signals such as mobile phone calls. Microwave transmitters and receivers on buildings and masts communicate with the mobile telephones which are in their range.
Certain microwave radiation wavelengths pass through the Earth’s atmosphere and can be used to transmit information to and from satellites in orbit.
Radio waves are used to transmit television and radio programmes. Longer wavelength radio waves are reflected from an electrically charged layer of the upper atmosphere. This means they can reach receivers that are not in the line of sight because of the curvature of the Earth’s surface.
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