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.
On this page
- Electromagnetic radiation
- Non-ionizing radiation
- Ionizing radiation
- Noise and sound (acoustical radiation)
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:
- radiofrequency waves
- microwaves
- infrared
- visible light
Sources of non-ionizing radiation
Non-ionizing radiation can come from natural and artificial sources.
Natural sources of non-ionizing radiation include:
- lightning
- light and heat from the sun
- the Earth's natural electric and magnetic fields
Artificial sources of non-ionizing radiation include everyday things such as:
- tanning beds
- microwave ovens
- wireless devices such as:
- cell phones
- cell phone towers
- Wi-Fi equipment
- radio and TV broadcast antennas
- lighting products such as:
- LED lights
- incandescent light bulbs
- compact fluorescent bulbs
- power lines and household wiring
- handheld lasers and laser pointers
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:
- some forms of electromagnetic radiation:
- high energy ultraviolet radiation
- X-rays
- gamma rays
- particle radiation such as:
- alpha particles
- beta particles (electrons)
- neutrons
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:
- nuclear energy
- medical devices such as:
- X-ray machines
- CT scanners
- Mammography
- Baggage X-ray screening devices
- Industrial devices used for scientific research and measurement
Find out more on the health effects of radiation.
Noise and sound (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:
- 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.
- 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.
- 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.