The electromagnetic spectrum
The electromagnetic spectrum groups together all electromagnetic waves depending on their frequency, wavelength or energy. It is split into several main categories which each have their specificities.
The electromagnetic waves that compose the spectrum do not need a physical medium to move: we are permanently surrounded by an electromagnetic field in the same way as we are surrounded by air.
The main broad categories of frequencies are as follows:
- Radio waves or hertzian waves: from 3 Hz to 300 MHz. This category concerns the waves that have the lowest frequencies of the spectrum. Relatively easy to transmit and receive via antennas, radio waves are used for the transmission of information (radio and television for example).
- Microwave: 300 MHz to 300 GHz. This category of waves uses slightly higher frequencies. They have the particularity to propagate like light and not be absorbed by the atmosphere as long as their frequency remains below 12 GHz. They are used for satellite transmissions, cell phone, internet, and for microwave ovens.
- Above 300 GHz: wave domains that emit at higher frequencies, such as X-rays or gamma rays, are used for different purposes (radiography, food preservation ...), given their very nature. energy.
There is also a category of waves a little apart, which is visible light. Indeed, all the waves that the human eye can perceive belong to a very small part of the electromagnetic spectrum. Just as the human ear can not perceive sounds that are too high or too high, our eyes can not perceive rays that have wavelengths smaller than 400 nm and larger than about 700 nm (or in terms of frequency, between 4.3x1014 and 7.5x1014 Hz).
The frequency of the wave also determines its color: the lower frequency radiations are red, while those of higher frequency are blue and violet. We can manipulate this light through optical instruments: lenses, prisms, etc ...
Given their many concrete applications, entire economic sectors rely on access to electromagnetic frequencies: mobile communications, digital terrestrial television, satellite links, transport, military industry or Internet of Things.
The role of the National Frequency Agency is to ensure, in close relationship with the assigns, the management of this spectrum, and more specifically frequencies ranging from 3kHz to 300 GHz, thus covering both radio waves and microphones. -ondes.
It contributes to the development of international regulations and the delimitation of frequency bands at the national level, authorizes and manages radio sites (from mobile phone relay antennas to radars), and controls the proper use of the spectrum on a daily basis.
The fabulous history of frequencies
On the occasion of ANFR's 20th anniversary ceremony, and to illustrate the stakes of the spectrum, ANFR presented a comic strip, "the fabulous history of frequencies", which illustrates the rise of wireless uses, from the discovery of electromagnetism to the present day.
This comic book is now available on our online store. To acquire it and discover the fabulous history of the frequencies go to our shop.
You can also consult it below: