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What are the Different Types of Radiation?

Artist’s interpretation of astronaut in space

Artist’s interpretation of astronaut in space (isitsharp, iStockphoto)

Artist’s interpretation of astronaut in space

Artist’s interpretation of astronaut in space (isitsharp, iStockphoto)

Let's Talk Science

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Learn about the different types of radiation, how they interact with atoms and how they can affect you.

Radiation is a type of energy that can travel through space. Sometimes it travels in the form of a wave. That’s called electromagnetic radiation. Sometimes, it travels as a beam of fast-moving particles. That’s called particle radiation. 

Radiation is all around you! And it’s been there all your life.

What is electromagnetic radiation?

Electromagnetic radiation (EMR) consists of waves. The waves contain electric and magnetic energy. 

The electromagnetic spectrum (EMS) includes different types of energy waves. At one end of the spectrum, there are very low energy waves. Radio waves are an example of low energy waves. At the other end of the spectrum, there are very high energy waves. Gamma rays are an example of high energy waves.

Electromagnetic Spectrum
The electromagnetic spectrum. High-energy gamma rays are on the far left and low-energy radio waves are on the far right (Let's Talk Science using an image by Inductiveload [CC BY-SA 3.0] via Wikimedia Commons).

Frequency and wavelength are used to describe EMR. Frequency refers to the number of waves per second. Wavelength refers to the distance between two adjacent wave peaks. The higher a wave’s frequency, the shorter its wavelength. For example, gamma rays have a very small wavelength and very high frequency. They also have a lot of energy!

There are seven natural forms of EMR. Gamma rays have the highest energy and shortest wavelength. Then come X-rays, ultraviolet light, visible light, infrared radiation and microwave radiation. Finally, radio waves have the lowest energy and longest wavelength.

You can only sense two parts of the EMS. You can feel infrared radiation and you can see visible light. Radio waves, X-rays and gamma rays can pass through your body. But you can’t see them or feel them. 

Electromagnetic radiation travels in little packets (quanta) of energy. These charge-less bundles of energy are called photons. They travel at the speed of light (2.998 × 108 m/s) in a vacuum.

How electromagnetic radiation interacts with the human body
How electromagnetic radiation interacts with the human body (Let’s Talk Science using an image by mohamed Hassan via Pixabay).

What is the difference between ionizing and non-ionizing radiation?

Radiation can be either non-ionizing or ionizing. 

  1. Non-ionizing radiation doesn’t have enough energy to ionize atoms or molecules. That means it can’t cause atoms to gain or lose electrons.

    There are several types of non-ionizing radiation. They include near ultraviolet light, visible light, infrared radiation, microwaves and radio waves. Even if it can’t ionize atoms, these types of radiation aren’t completely harmless. For example, microwaves have enough energy to cook your food. And ultraviolet light can give you a sunburn. 

  1. Ionizing radiation has enough energy to remove electrons from atoms. This creates ions.

    Ionizing radiation includes far ultraviolet light, X-rays and gamma rays. These types of high-energy radiation can cause cancer or even kill cells directly. That’s why you wear a lead apron when getting a dental X-ray.

    The amount of radiation in a single X-ray isn’t harmful! But the radiation from a large number of X-rays could be dangerous. That’s why people who operate X-ray equipment leave the room.

x-ray technician/technicien en radiologie
X-ray technician looking at a dental x-ray in a room separate from the x-ray machine (Source: Elías Alarcón via Pixabay).

What is particle radiation?

Particle radiation is made up of atomic or subatomic particles. These particles include protons, neutrons and electrons. They all have kinetic energy. That’s the energy is the energy an object has when it’s in motion. 

Both alpha particles and beta particles produce ionizing radiation. The charge they carry can remove electrons from atoms. They can also interact directly with an atom’s electrons through Coulombic forces.

Alpha particles consist of two protons and two neutrons. These particles are large, slow-moving and positively charged. An alpha particle is identical to the nucleus of a helium atom. 

Beta particles are small and fast-moving. They can have a positive charge (positrons) or a negative charge (electrons). 

Alpha and beta particles
Each alpha particle has two protons and two neutrons. A beta particle can be a high speed electron or positron (©2019 Let’s Talk Science).

Each alpha particle has two protons and two neutrons. A beta particle can be a high speed electron or positron (© 2019 Let’s Talk Science).

Neutrons are particles located in the nucleus of an atom. Unlike protons and electrons, they are not charged.

Neutron radiation is a type of indirectly ionizing radiation. It’s made up of free neutrons that have been released from atoms. 

Free neutrons can react with the nuclei of other atoms to form isotopes. These isotopes can then emit radiation, such as gamma rays. Neutron radiation is called indirectly ionizing radiation. That’s because it doesn’t ionize atoms in the same way as charged particles. 

Inelastic scattering of neutrons
A neutron strikes a larger nucleus in an inelastic collision. The energy gained by the nucleus is released as Gamma ray photons. The neutron still has a considerable amount of energy (©2019 Let’s Talk Science).



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Mirion Technologies. (2015, March 31). What is radiation?

National Cancer Institute. (n.d.). NCI dictionary of cancer terms: Non-ionizing radiation.

Ontario Ministry of Labour. (2013, November). Personal protective equipment in radiology.

United States Nuclear Regulatory Commission. (2017, October 2). Radiation Basics.