# Electromagnetic energy

The electromagnetic energy is the amount of energy stored in a region of space that can be attributed to the presence of an electromagnetic field , and is expressed in terms of the intensity of the magnetic field and electric field . At one point in space the electromagnetic energy density depends on a sum of two terms proportional to the square of the field strengths.

## Summary

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• 1 Electromagnetic energy diffusion
• 2 Phenomena associated with electromagnetic energy
• 3 Electromagnetic spectrum
• 4 Sources

## Electromagnetic energy diffusion

Electromagnetic energy propagates through space in the form of radiation, which is a combination of oscillating electric and magnetic fields. Electromagnetic radiation can manifest itself in various ways such as radiated heat, visible light, radiofrequency, X-rays, or gamma rays. Unlike other types of waves, such as sound, that need a material medium to propagate, electromagnetic radiation can propagate in a vacuum. In the 19th century it was thought that there was an undetectable substance, called ether, that occupied the vacuum and served as a means of propagating electromagnetic waves.

## Phenomena associated with electromagnetic energy

There are many physical phenomena associated with electromagnetic energy that can be studied in a unified way, such as the interaction of electromagnetic waves and charged particles present in matter. Among these phenomena are for example visible light , heatradiated, radio and television waves or certain types of radioactivity to name a few of the most prominent phenomena. All these phenomena consist of the emission of electromagnetic radiation in different frequency ranges (or equivalently different wavelengths), the frequency or wavelength range being the most used to classify the different types of electromagnetic radiation. The ordering of the various types of electromagnetic radiation by frequency is called the electromagnetic spectrum.

## Electromagnetic spectrum

Considering its wavelength, electromagnetic radiation receives different names, and varies from energetic gamma rays (with a wavelength of the order of picometers) to radio waves (wavelengths of the order of kilometers), passing through the visible spectrum (whose wavelength is in the range of tenths of a micrometer). The entire range of wavelengths is what is called the electromagnetic spectrum. The visible spectrum is a tiny range from the wavelength corresponding to the violet color (approximately 400 nanometers) to the wavelength corresponding to the red color (approximately 700 nm).

In telecommunications, waves are classified by means of an international frequency agreement depending on the use for which they are intended, as shown in the table. In addition, a special type called microwaves should be considered, since their frequency range is between 1 GHz and 300 GHz. That is, wavelengths between 30 centimeters to 1 millimeter, which have the ability to traverse the Earth’s ionosphere, allowing satellite communication.

Classification of waves in telecommunications

Acronym            Rank                Denomination                             Employed             VLF 10 kHz to 30 kHz Very low frequency Long range radio         LF 30 kHz to 300 kHz Low frequency Radio navigation         MF 300 kHz to 3 MHz Medium frequency Medium wave radio         HF 3 MHz to 30 MHz High frequency Shortwave radio        VHF 30 MHz to 300 MHz Very high frequency TV, radio        UHF 300 MHz to 3 GHz Ultra high frequency TV, radar, mobile phone        SHF 3 GHz to 30 GHz Super High Frequency Radar        EHF 30 GHz to 300 GHz Extremely High Frequency Radar