About radiation

Radiation is energy that comes from a source and travels through space as waves or particles. There are different types of radiation, each with their own characteristics or properties.

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Electromagnetic radiation

Electromagnetic radiation refers to energy that travels in waves through space at the speed of light. Electromagnetic radiation can be either ionizing or non-ionizing radiation depending on its frequency.

Frequency describes how quickly the energy waves move up and down. The higher the frequency of the radiation the higher its energy. Frequency is expressed in Hertz (Hz), or how many times a wave goes up and down in 1 second.

Wavelength is the distance between two consecutive peaks or troughs of a wave. The longer the wavelength of the radiation, the lower its energy. Wavelength is expressed in distance (mm, cm).

Frequency and wavelength are directly related. As wavelength increases, or the distance between the peaks increases, the frequency, or the number of waves, decreases. Therefore as wavelength increases, the frequency of the radiation decreases.

Frequency = 1/wavelength

Non-ionizing radiation

Non-ionizing radiation is also a type of electromagnetic radiation. This type of radiation does not have enough energy to detach electrons.

Non-ionizing radiation includes:

Sources of non-ionizing radiation

Non-ionizing radiation can come from natural and artificial sources.

Natural sources of non-ionizing radiation include:

Artificial sources of non-ionizing radiation include everyday things such as:

Ionizing radiation

Ionizing radiation is a type of radiation that can detach electrons from, or ionize, other atoms as they pass through matter. It includes electromagnetic waves and subatomic particles. Examples of ionizing radiation include:

Sources of ionizing radiation exposure

Natural sources of ionizing radiation include radiation in the environment from rocks and soil as well as cosmic radiation from space. These sources of radiation are referred to as "background" radiation.

Artificial sources of ionizing radiation include:

Find out more on the health effects of radiation.

Noise (acoustical radiation)

Acoustical radiation is energy that is produced by a vibrating source and travels through air, water and solid materials in the form of waves. These vibrations produce sound.

Sound can be separated into 3 categories:

  1. Infrasound is the range of low frequency sound waves that humans do not typically hear. Scientists measure infrasound levels to detect earthquakes and to forecast volcano eruptions.
  2. Audible sound is the range of medium frequency sound waves that most humans can hear. Listening to sound that is too loud can damage your hearing.
  3. Ultrasound is the range of high frequency sound waves that humans typically do not hear. Medical professionals use ultrasound to create an image of tissues inside of the body.

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