The Electromagnetic Spectrum



The electromagnetic spectrum is the entire range of electromagnetic radiation according to the wavelength or frequencies. It has a range of frequencies from 1Hz to Hz. The waves in order of increasing frequencies are radio waves, microwaves, infrared rays, visible light, UV rays, X-rays and gamma rays.Among these range, the frequencies between Hz to Hz are used for communication.

The following diagram shows the electromagnetic spectrum. The first figure gives the full range of frequency spectrum while the second figure elaborates that part of the spectrum which can be used for data communication −

The Electromagnetic Spectrum

The section of the spectrum in the range of radio waves and microwaves has been divided into a number of frequency bands as officially referred by ITU (International Telecommunication Union). These bands are rated from VLF (Very Low Frequency) to EHF (Extremely High Frequency).

The frequency bands and their uses in communication is tabulated as follows −

Band Name Full Forms Frequency Range Propagation Uses
ELF Extremely Low Frequency 30 – 300Hz Ground Power line frequencies
LF Low Frequency 3 – 300 KHz Ground Marine Communications, communication over twisted pair
MF Medium Frequency 300KHz –3MHz Sky AM radio, communication over coaxial cables
HF High Frequency 3 – 30 MHz Sky Aircraft and ship communications
VHF Very High Frequency 30 – 300 MHz Sky and Line – of - Sight FM radio, TV
UHF Ultra High Frequency 300 MHz – 3GHz Line – of - Sight TV, cellular phone
SHF Super High Frequency 3 – 30 GHz Line – of - Sight Satellite, microwave links
EHF Extremely High Frequency 3 – 300GHz Line – of - Sight Radar, satellite
Infrared Infrared Rays 300 Ghz – 400THz Line – of - Sight Consumer electronic goods
Visible Light Visible Light rays 400 THz – 900 THz Line – of - Sight Fiber optic communications

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