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Analyse information to identify the electromagnetic spectrum range utilised in modern communication technologies.
The production and detection of electromagnetic waves at frequencies other than the visible range has produced a communications revolution. An image of the electromagnetic spectrum is shown on the right. The parts of the electromagnetic spectrum that we use for communication include radio waves, microwaves, infra-red, visible light and ultraviolet.
Radio waves have the longest wavelengths and are used extensively for communication. Short wavelengths ranging from 30cm ?V 3m are used for mobile phones. Long and medium wavelength radio waves can diffract around large obstacles, so they can be received even when there is no direct ??line of sight?? between the transmitter and the receiver. Hence, medium wavelengths ranging from 3m-100m are used in FM radio and television transmission and long wavelength radio waves ranging from 100m-500m are used for AM radio.
Microwaves have wavelengths ranging from 1 millimetre to 30 centimetres. The modulation of microwaves enables them to transfer information. The main disadvantage of microwaves is that they require a line of sight connection from one antenna to the next. Mobile phones use microwaves for their transfer of energy and information. Interference can easily occur if there is something in the line of sight making microwave signals less reliable. With phone signals on frequencies around 900MHz, transmission can be across distances of up to 100km. Microwaves are also used in radar, satellite communications, relay stations and towers.
Many electronic remote controls for such as video, television, garage doors and remote-control wireless connections to computers, use infra-red radiation to transfer the signal from the control device to the item.
Without the need of wiring, data can be easily broadcasted over relatively short distances.
Other applications of infra-red radiation include switchboards in large buildings, which are photographed using infra-red cameras to check for hot spots that might indicate dangerous electrical faults or if circuit overloading is occurring. This heats up causing the wire to give off infra-red radiation. In the telecommunications industry, infra-red lasers send information down optical fibres. Also, satellite infra-red images can give farmers information on the health of crops. Aeroplanes that carry infra-red detectors can identify forest-fire hotspots even when hidden by a curtain of smoke.
The use of reflection and visible signalling, such as smoke signals, was almost certainly the first long-distance method of communication. With a wavelength of 400-700nm, its applications include fibre optic telecommunications, remote sensing of vegetation patterns from satellite and aeroplane surveys. In particular, the use of reflection and visible signalling in smoke signals was the first long-distance method of communication.
Ultraviolet radiation has wavelengths of 10-400nm. UV light can cause ionisation of atoms, leading to the sterilization of hospital equipment. In terms of communication, it is used in making astronomical observations.
Part of the Electromagnetic Spectrum Use in modern communication technologies
Radio Waves Television, FM and AM radio, radar
Microwaves Mobile phone signals, radar, satellite communications
Infra-red Electronic remote controls, wireless connections to computers, telecommunications ?? infra-red lasers
Visible Light Fibre optic telecommunications, remote sensing from satellite and aeroplane surveys, smoke signals, identification of objects by their visible colour
Ultraviolet Astronomical observations
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