Microwaves and radio waves are used to communicate with satellites. Microwaves pass straight through the atmosphere and are suitable for communicating with distant geostationary satellites, while radio waves are suitable for communicating with satellites in low orbit.
Radio waves and microwaves are types of electromagnetic radiation [electromagnetic radiation: Energy travelling as waves in the form of changing electrical and magnetic fields.] . Both have communication uses. Radio waves are used to transmit television and radio programmes, while microwaves are used for mobile phones and Wi-Fi. However, they have different properties:
Radio waves have longer wavelengths [wavelength: The length of a single wave, measured from one wave crest to the next.] and are reflected by the ionosphere [ionosphere: Ionised region of the Earth's upper atmosphere.] (part of the Earth’s atmosphere).
Microwaves have shorter wavelengths and pass through the Earth’s atmosphere.
The way that electromagnetic waves behave in the atmosphere depends on their frequency. The table below summarises this.
|Increasing frequency →|
|Frequency||Less than 30 MHz||30 MHz – 30 GHz||More than 30 GHz|
|Behaviour||Reflected by the ionosphere||Waves pass straight through the atmosphere||Rain, dust and other atmospheric effects reduce the strength of the signal due to absorption and scattering|
|Low amounts of energy needed||Carbon dioxide is produced as a by-product||Less land needed||Higher amounts of energy needed|
|Wavelength||More than 10 m||10 m – 10 cm||Less than 10 cm|
|Decreasing wavelength →|
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