Do you remember ions from GCSE Chemistry? In case you've forgotten, ions are charged particles.
Every atom contains an equal number of positively charged protons and negatively charged electrons.
Removing an electron from an atom converts it into a positively charged ion.
Ionisation radiation is named so because it ionises atoms it passes through!
To ionise something is to turn a regular atom into an ion.
Ready to learn more? Read on!
Ionising Radiation: Definition
Let's start by recapping radiation itself.
Radiation is the process of emitting energy through waves or particles.
Now that we're familiar with the term, let's learn the definition of ionising radiation.
Ionising radiation is a form of radiation with enough energy to remove electrons from atoms it passes through.
Ionising radiation turns regular atoms into positive ions.
Ionising vs Non-Ionising Radiation
Not all radiation is ionising. Let's look back to GCSE Physics and the electromagnetic spectrum.
The electromagnetic spectrum covers the range of wavelengths of radiation.
The wavelengths of radiation decrease from the left side to the right side.
Property | Definition | Left Side | Right Side |
Wavelength | The length of a single wave (measured in metres). | Longer | Shorter |
Frequency | The number of waves produced per second (measured in Hertz). | Lower | Higher |
Energy | The amount of energy carried by the wave. | Lower | Higher |
Regardless of wavelength, all electromagnetic radiation travels at the same speed: 300,000 kilometres per second.
The energy of radiation is directly proportional to its frequency; thus inversely proportional to its wavelength.
Energy of an electromagnetic wave can be calculated using the equation E = f h, where:
- E: energy
- f: wavelength
- h: Planck's constant (6.62607015 x 10-34 Joule-seconds)
Don't worry, you don't have to do any calculations using Planck's constant during your exams!
There are seven types of electromagnetic radiation. In order of decreasing wavelength, (and increasing energy) they are:
Radio Waves
Microwaves
Infrared Radiation
Visible Light
Ultraviolet Radiation
X-rays
Gamma Rays
Radio waves, microwaves, infrared radiation, and visible light are considered non-ionising. They have a lower frequency, so they have less energy than ionising radiation.
Ultraviolet radiation, X-rays, and gamma rays are considered ionising. Unlike non-ionising radiation, ionising radiation can alter molecules within our bodies.
Types of Ionising Radiation
We've learned that the three types of ionising radiation are ultraviolet radiation, X-rays, and gamma rays. Let's go into detail about each type.
Radiation | Wavelengths | Frequencies (Hertz) | Uses |
Ultraviolet | 400 nm to 1 nm | 1015 to 1017 | - Fluorescent lamps
- Tanning beds
- Detecting forged banknotes
|
X-ray | 1 nm to 1 pm | 1017 to 1020 | - Detecting bone fractures
- Airport security
- Revealing counterfeit art
|
Gamma | < 1 pm | 1020 to 1024 | - Radiotherapy
- Nuclear power
- Pasteurisation
|
Nanometres (nm): 10-9 metres
Picometres (pm): 10-12 metres
Uses and Examples of Ionising Radiation
High-energy ionising radiation is important in a range of industries.
Nuclear Weapons
When a free neutron hits the nucleus of a radioactive material (e.g. uranium), it sets off a chain reaction of nuclear decay, releasing neutrons and large amounts of ionising radiation. Nuclear weapons such as atomic bombs exploit chain reactions of nuclear fission, producing an atomic explosion.
Nuclear fission is a reaction where the nucleus of an atom splits into multiple smaller nuclei, releasing ionising radiation.
Nuclear weapons have only been used twice. In August 1945, the US dropped two atomic bombs on the Japanese cities of Hiroshima and Nagasaki. The bombs wiped out both cities' infrastructure, and killed up to 215,000 people – including those directly from the bomb and those suffering long-term health problems associated with radiation.
Figure 2 – The atomic bomb dome in Hiroshima is the only structure left standing after the detonation of nuclear weapons in 1945. Source: unsplash.com
Nuclear Power
Nuclear power also exploits the chain reactions of nuclear fissions, but instead using the energy produced to generate electricity. The energy released from the nuclear decay of uranium or plutonium is used to convert water into steam. The steam travels through turbines, which drives a generator, converting the turbine's kinetic energy into electricity.
Ship Propulsion
Ionisation radiation could present a carbon-free propulsion source for ships. Controlled chain reaction of nuclear decay releases large amounts of energy. Technology on board the ship transfers this energy to a coolant, which is used to generate propulsion power.
Manufacturing and Industry
Ionising radiation is frequently used in manufacturing and industry, including:
Disinfecting drinking water
Checking for defects in metallic castings and welds
Locating fossil fuels and minerals for extracting
Making signs reflective
Producing non-stick cookware
Creating wrinkle-free clothing
Healthcare
Gamma radiation is used to sterilise medical equipment without using heat. It's also important in many diagnostic and treatment practices.
X-rays are used to detect and diagnose broken bones.
Radiotherapy uses targeted doses of gamma radiation to destroy tumours in the body.
Tracers containing radioactive isotopes are used to make soft tissues show up in medical imaging, and indicate tissue blockages.
Agriculture and Food Production
The agriculture industry exposes plants to ionising radiation to control insect populations, thus reducing the demand for polluting pesticides.
Fresh fruit is often exposed to ionising radiation from an isotope of cobalt-60. Gamma rays emitted by the cobalt will destroy any bacteria on the fruit, without contaminating or damaging the fruit in any way.
Irradiation pasteurisation exposes milk to ionising radiation, killing bacteria without the use of heat.
Dangers of Ionising Radiation
Exposure to ionising radiation can cause health problems. The high-energy radiation removes electrons from atoms, creating unstable molecules called free radicals. Free radicals are highly reactive, causing damage to the body's cells and DNA:
Health Consequences Caused by Free Radicals
Cell damage caused by free radicals results in a range of health consequences.
Radiation Sickness
Exposure to an acute dose of ionising radiation can cause radiation sickness. Symptoms include:
Cancer
Free radical damage may trigger carcinogenesis. Alternatively, damaged cells may be unable to repair themselves, leading to cancer in the long term.
Radiation doses over 100 mSv (millisieverts) have been associated with increased cancer risk in later life.
Even high levels of exposure to sunlight (containing UV radiation) is associated with skin cancer in later life.
Figure 3 – Metastatic melanoma cells under a microscope. This condition occurs when cancerous melanoma cells (caused by exposure to ionising ultraviolet radiation) spread to the rest of the body. Source: unsplash.com
Heritable Effects
If pregnant women are exposed to ionising radiation, it can impact the foetus. Effects include stunted growth, deformities, brain abnormalities, and an increased risk of cancer.
Ionising Radiation: UK Regulations
Due to the health risks of ionising radiation, it's regulated carefully.
The Ionisation Radiation Regulations 2017 (shortened to IRR17) is the main legislation regulating exposure to ionising radiation in the UK. Any employer or industry where ionising radiation is used must comply with the IRR17.
All employers are required to keep exposure to ionising radiation as low as possible. Exposures must not exceed specified dose limits of:
20 mSv in a calendar year
Or 100 mSv over five consecutive years, with a maximum dose of 50 mSv in a single year
Additionally, it's important to note that nuclear power generates large amounts of radioactive waste. This needs to be disposed of carefully to prevent contamination.
I hope that this article has explained ionisation radiation for you. Remember that it is a form of radiation with enough energy to remove electrons from atoms it passes through. Ionising radiation is useful in a range of industries. However, exposure to large amounts of ionising radiation can be dangerous, so it is regulated carefully.
Ionising Radiation - Key takeaways
- Ionising radiation is a form of radiation with enough energy to remove electrons from atoms it passes through. It has more energy, a higher frequency, but a lower wavelength than non-ionising radiation.
- Types of ionising radiation include ultraviolet radiation, X-rays, and gamma rays.
- Uses of ionising radiation include nuclear weapons, nuclear power, ship propulsion, manufacturing and industry, healthcare, and agriculture and food production.
- Exposure to ionising radiation leads to the formation of free radicals, which damage cells. The associated cell damage leads to health problems such as radiation sickness, cancer, and heritable effects.
- As a result, ionising radiation is regulated carefully using the Ionisation Radiation Regulations 2017. Individuals working with radiation must not exceed specified dose limits, and radioactive waste must be disposed of carefully.
1. American Museum of Natural History, Constant Speed, 2022
2. History.com, Bombing of Hiroshima and Nagasaki, 2022
3. Patrick J. Kiger, What Is Planck's Constant, and Why Does the Universe Depend on It?, How Stuff Works, 2019
4. UK Government, The Ionising Radiations Regulations 2017, 2017
5. University of Tennessee, The EM Spectrum, 2022
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