What is Radiation? - Definition, Causes & Effects

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  • 0:00 The Nature of Radiation
  • 1:04 Ionizing &…
  • 2:03 Causes of Radiation
  • 5:20 Uses for Radiation
  • 7:16 Dangers of Radiation
  • 9:02 Lesson Summary
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Lesson Transcript
Damien Howard

Damien has a master's degree in physics and has taught physics lab to college students.

Expert Contributor
Christianlly Cena

Christianlly has taught college physics and facilitated laboratory courses. He has a master's degree in Physics and is pursuing his doctorate study.

Learn about the reality and pervasiveness of radiation in our world. Discover some of the causes of radiation, and find out about the risks and rewards of harnessing it for our use.

The Nature of Radiation

Radiation may bring to mind the superheroes and monsters of comic books and movies, but radiation is very real and all around us! In fact, you are currently being bombarded by radiation. It might be coming from the sun, various electronic devices you own, or even the food in your kitchen. If you have ever eaten a banana, you have eaten a radioactive material. The good news is that the vast majority of radiation you are exposed to is relatively harmless.

Whether or not radiation can harm you depends on the type of radiation, the dosage you come in contact with, and the length of the exposure. Here we'll go over the different types of radiation, their causes, uses to us, and dangers. Before we get started, you need to know what exactly radiation is in general. Radiation can be defined as the transmission of energy from a body in the form of waves or particles. This can encompass anything from dangerous radiation created by a nuclear power plant to the harmless light created by a flashlight.

Ionizing and Non-Ionizing Radiation

Before we go any further, let's cover some basic terms. Ionization is the process in which an atom either loses or gains an electron. Since electrons are negatively charged, this process will take an atom, which normally has no charge, and give it either a positive or negative charge depending on whether it lost or gained electrons. An atom that has a charge to it is called an ion.

So the difference between ionizing radiation and non-ionizing radiation is that ionizing radiation has enough energy to strip electrons off of atoms, and non-ionizing radiation does not have enough energy to strip electrons off of atoms. One of the easiest ways to visualize the difference between these two is to look at the frequency spectrum for light. As the frequency goes up, so does energy, so we can see the energy cut off for light where it goes from non-ionizing to ionizing radiation is within the ultraviolet light spectrum. Now let's look at the causes of both types of radiation.

Causes of Radiation

Non-ionizing radiation is limited to the lower energy range electromagnetic radiation, which is more commonly known as light. However, the light we can see with our eyes, visible light, is only a small section of the electromagnetic radiation spectrum as seen here.

Electromagnetic radiation spectrum
frequency spectrum of electromagnetic radiation

All types of light are a type of radiation. The most common way this type of radiation is created in our universe is by stars like our sun. Inside stars, hydrogen atoms are constantly bouncing around, and under great pressure and temperature. Two hydrogen atoms can collide and form a helium atom. This is a process known as nuclear fusion. In this fusion process, energy is given off as a byproduct. This energy is the electromagnetic radiation created by the stars.

On a smaller scale, a light bulb is a good second example of how non-ionizing radiation can be created. In a light bulb, electricity is passed through a tungsten filament surrounded by an inert gas that keeps the filament from catching fire. The electrons put into the filament constantly collide with the tungsten atoms, causing them to vibrate. This atomic vibration then gives off radiation in the form of heat and light. Vibrating atoms are another common cause of non-ionizing radiation.

Given that ionizing radiation is high-energy radiation and non-ionizing radiation is low-energy radiation, it might have seemed strange to you that nuclear fusion is a process that creates low-energy radiation. In fact, nuclear fusion in stars is a special case. It creates both high and low energy radiation.

The types of ionizing radiation most commonly talked about are those created by radioactive decay. This is when unstable atoms try to rearrange themselves in some way to change their energy and become stable. The three most common types of this kind of radiation are alpha decay, beta decay, and gamma decay.

In alpha decay, the atom changes its energy by spitting out two neutrons and two protons, which happens to be the nucleus of a helium atom. In beta decay, the atom spits out either an electron or a positron, which is the antimatter counterpart to an electron. In gamma decay, unlike the other two, the atom does not actually remove a piece of itself. Instead, the atom tries to change its energy by rearranging the neutrons and protons in its nucleus. As a side effect of this, it releases an extremely high energy photon called a gamma wave.

Much like the flashlight in non-ionizing radiation, ionizing radiation can also be created artificially. One example would be nuclear fission in a power plant. Where nuclear fusion combined two atoms together, nuclear fission breaks one apart. By bombarding a specifically prepared uranium rod with neutrons, a nuclear reactor is capable of breaking the uranium atom apart. This process releases a large amount of energy in the form of radiation. The energy can then be harnessed to create electrical power.

Uses for Radiation

So what are some uses for radiation?

Non-ionizing radiation is the kind that's all around us in the various electronic devices we use. Microwaves are used in the aptly named microwave for cooking meals. Radio waves transmit voices across the world into and out of our car radios. The radiation used for cell phones falls somewhere in between the radio and microwave spectrum and is used in a similar fashion to radio waves. You might at some point have seen on television a police chase where a helicopter uses an infrared radiation in a camera to see heat sources and spot a suspect in the dark. But, did you know your television remote is using that same infrared to communicate with the TV when you press buttons on it? Finally, we even use low energy ultraviolet radiation in tanning beds.

Ionizing radiation is far less commonly used, but it still has its place. One such use is for carbon dating. In every living thing, there are carbon-14 atoms, an unstable atom that experiences beta decay. While we live, the supply of this atom is replenished in our bodies, but when someone dies, the supply stops. Knowing how fast carbon-14 decays, archaeologists can check how much remains in a person, animal, or plant to get an estimate on how old it is.

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Additional Activities

Modified True or False Exercise on Radiation


Check your knowledge of the lesson about the definition, causes, and effects of radiation by determining whether the following statements are true or false. For this activity, print or copy this page on a piece of paper. Write TRUE if the statement is valid and FALSE if otherwise on the blank space provided. If the statement is FALSE, write down the word or phrase that makes it wrong.

_____1. Radiation is a type of energy transfer in the form of electromagnetic waves that travel through space.

_____2. Visible light constitutes a large fraction of the electromagnetic spectrum.

_____3. The frequency and energy of a light wave are directly proportional; as the frequency of light increases, the energy increases as well.

_____4. Non-ionizing radiation has less energy to strip electrons off atoms, making it safe for humans.

_____5. A common side effect of overexposure to beta decay radiation is skin cancer.

_____6. Radiation has been employed in cancer treatment because of its precision in eliminating cancer cells.

_____7. Any process that leads to the separation of a neutral atom into charged particles is known as ionization.

_____8. An alpha decay leads to a release of extremely high energy photons.

_____9. Nuclear fusion involves the fusion of lighter nuclei atoms to form a single heavier atom.

_____10. In stars, nuclear fusion in their core only creates high-energy radiation.

Answer Key


2. FALSE, large fraction


4. FALSE, safe

5. FALSE, skin cancer



8. FALSE, alpha decay


10. FALSE, only creates high-energy radiation

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