Physics of Radiation – Introduction

Since the 19^th century there have been tremendous advances in the discovery and scientific theories relating to matter and radiation (in particular, light).  An understanding of the basic physical properties of radiation, now almost common knowledge, has enabled mankind to develop important technologies that apply to all aspects of life.

Current theories and scientific experiments have indicated that radiation has been an integral part of the universe since its inception.  Professor Albert Einstein's famous theorem expressing the equivalence between matter and energy, demonstrates the essential nature of the physical properties of radiation to our very existence.

Radiation and the world of physics

In modern physics, the term 'radiation' encompasses several fields, including elementary particle physics, nuclear physics, atomic physics, and molecular physics.

The exposure of humans to radiation relates to physical phenomena at the level of the atom, the molecule, and biological composition.  In our daily lives we are exposed to different types of radiation, from both natural and man-made sources.  Humans use a variety of sources of radiation in numerous fields, such as in radio communication, or in medicine - for diagnosis and therapy.

As science and technology advance rapidly, we require a greater variety of sources of radiation.  What are the various types of radiation, and by which physical properties do we distinguish between them?  On the TNUDA website we will try to provide brief but comprehensive answers to this question.

The word radiation usually refers to electromagnetic radiation – energy provided by the electro-magnetic activity of particles carrying electrical charges. Electromagnetic radiation is also expressed as fields spreading through space in the form of waves.  The physical properties of electro-magnetic radiation are: frequency, wave length, wave amplitude, and intensity.

All types of electromagnetic radiation – radioactive, ultraviolet, infra-red, visible light, radio emissions, up to the very long wave radiation (such as the electric power network) – are defined by a scale of frequencies (or wave lengths) known as the electromagnetic spectrum.

The electromagnetic spectrum

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Is radiation essential?

How important is electromagnetic radiation to our existence?  Is life on earth possible without electromagnetic radiation?  The answer is almost beyond comprehension:  according to physical theories, if someone in the universe were to turn off electromagnetic radiation by a flick of a hidden switch, all matter known to us – atoms, molecules and solid matter – would disintegrate at once and be transformed into a collection of basic particles (electrons and atomic nuclei).  Clearly, we would also disappear immediately.  Why? Because according to the most basic physics, electromagnetic radiation represents electro-magnetic interaction, and its disappearance would entail the disappearance of the forces that bind the electrons in the atom.  Therefore, our very existence is impossible without electromagnetic radiation.

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Types of radiation and their effect on our lives

How vital are the various types of radiation to our existence? Let us see:  solar radiation, for instance, constitutes the source of energy for life on earth.  Solar energy includes various types of radiation, among which are visible light and ultraviolet and infrared radiation.

Radio frequency (RF) refers to another type of radiation.  Examples of RFapplications are cellular phones, television and Wi-Fi transmitters.  Another type of radiation is emitted by electric currents flowing through the electric power grid.  This radiation is referred to as electric and magnetic fields, having extremely low frequencies.

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What else should we know?

On the TNUDA website you will find more information on the properties of radiation.  We focus mainly on non-ionizing radiation, including its various types and sources.  You can obtain information about the physical properties of systems and appliances such as antennas, cellular communication networks, mobile phones, various wireless devices, electric power grids and electrical appliances, as well as information on measuring radiation levels, and many additional issues.

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References

Juliana H. J. Mortenson, The Fundamental Physics of Electromagnetic. .Waves ,  Vitaliy Zhurbenko (editor), ISBN 978-953-307-304-0, Published: June 21, 2011 under CC BY-NC-SA 3.0 license.