# Electromagnetic radiation: definition, characteristics and types

Electromagnetic radiation is a disturbance of an electric field and a magnetic field that propagates in space.

Electromagnetic radiation can propagate in a vacuum, such as interplanetary space, in less dense media, such as the atmosphere, or in guiding structures, such as waveguides.

Gamma radiation is a type of very high frequency electromagnetic radiation. Gamma radiation is generally produced by radioactive elements or subatomic processes or by astrophysical phenomena.

The range of all possible electromagnetic radiation is what is known as the electromagnetic spectrum. The different types of electromagnetic radiation that can form an electromagnetic spectrum are:

• Microwave.

• Visible light (or visible spectrum).

• X-rays.

• Gamma rays.

The three characteristics that determine electromagnetic radiation are frequency, electromagnetic wavelength, and polarization.

The wavelength is directly related to the frequency through the (group) propagation velocity of the radiation. The group propagation speed of electromagnetic radiation in a vacuum is equal to the speed of light, in other environments this speed is less.

High-energy physics deals with harsh electromagnetic radiation at the shortwave end of the spectrum. According to modern concepts, at high energies, electrodynamics ceases to be independent, combining into a theory with weak interactions, and then, at even higher energies, as expected, with all other fields of measurement.

There are theories that differ in details and degrees of generality, which allows modeling and studying the properties and manifestations of electromagnetic radiation. The most fundamental of the complete and verified theories of this type is quantum electrodynamics.

Some characteristics of electromagnetic waves from the point of view of the theory of oscillations and the concepts of electrodynamics are:

• The presence of three mutually perpendicular vectors (in vacuum): wave vector, electric field vector E and magnetic field vector of intensity H.

• Electromagnetic waves are transverse waves in which the electric and magnetic field force vectors oscillate perpendicular to the direction of wave propagation, but they differ significantly from water waves and sound in that they can be transmitted from a source to a receiver. , even through a vacuum.

## Effects on human health

The effects of electromagnetic radiation on living beings depend above all on two main factors:

• the type of radiation exposure (radiation intensity, duration of exposure, part of the body exposed, etc.)

The amount of absorbed radiation is measured in grays, one gray corresponds to the absorption of one joule of radiated energy by one kilogram of matter. Another unit of measurement used in the field of nuclear energy is the sievert.

Regarding the frequency of radiation, it usually differentiates between ionizing and non-ionizing radiation.

### Ionizing radiation: what is it and what effects does it have?

Ionizing radiations are those that have a frequency high enough to ionize the atoms or molecules of the exposed substances.

This type of radiation is capable of modifying the chemical structure of the substances on which it affects and can produce long-term biological effects on living beings. An example of this alteration would be the modification of the DNA of cells that can lead to cancer.

As a curiosity, Hisashi Ouchi, the man who has received the highest dose of ionizing radiation in the world, received between 10 and 20 Sieverts.

X-rays and gamma radiation would be two examples of highly ionizing electromagnetic radiation.

### Non-ionizing radiation: what is it and what effects does it have?

Non-ionizing radiations are those that do not have enough frequency to cause ionization of exposed materials.

As an example of non-ionizing radiation, microwaves or radio waves can be mentioned. This type of radiation does not have sufficient energy to directly cause DNA mutations and therefore probably cannot initiate carcinogenesis but could be promoters.

From the point of view of its effects on health, non-ionizing radiation can be classified into three large groups:

• Low Frequency Electromagnetic Fields (ELF): Range 3 to 30,000 Hz).

• Radio frequency and microwave fields: range 30 kHz - 300 GHz.

• Optical radiation: from infrared light to ultraviolet light.

## Uses and applications

In general, two macro families of applications can be distinguished: