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- Alpha and beta radiation = particle radiation (caused by breaking of an atom)
- Gamma radiation = electromagnetic radiation (caused by movement of electrical charges)
What is alpha radiation?
Alpha radiation is composed of fast-moving helium nuclei ejected from the nucleus of heavy unstable atoms due to electromagnetic and strong interactions.
Alpha particles consist of two protons and two neutrons and have a travel range of up to a few centimetres in the air. The process of producing alpha particles is called alpha decay.
Although these particles can be absorbed by metal foils and tissue paper, they are highly ionising (i.e. they have sufficient energy to interact with electrons and detach them from atoms). Among the three types of radiation, alpha radiation is not only the least penetrating with the shortest range but is also the most ionising form of radiation.
Alpha decay
During alpha decay, the nucleon number (sum of the number of protons and neutrons, also called mass number) decreases by four, and the proton number decreases by two. This is the general form of an alpha decay equation, which also shows how alpha particles are represented in isotope notation:
\[^{A}_{Z}X \rightarrow ^{A-4}_{Z-2}Y+^{4}_{2} \alpha\]
The nucleon number = number of protons + neutrons (also called the mass number).
Some applications of alpha radiation
Sources emitting alpha particles have a variety of uses nowadays due to the unique properties of alpha particles. Here are some examples of these applications:
Alpha particles are used in smoke detectors. The emission of alpha particles generates a permanent current, which the device measures. The device stops measuring a current when smoke particles block the current flow (alpha particles), which sets off the alarm.
Alpha particles can also be used in radioisotopic thermoelectrics. These are systems using radioactive sources with long half-lives to produce electrical energy. The decay creates thermal energy and heats a material, producing current when its temperature increases.
Research is being conducted with alpha particles to see whether alpha radiation sources can be introduced inside a human body and directed towards tumours to inhibit their growth.
What is beta radiation?
Beta radiation consists of beta particles, which are fast-moving electrons or positrons ejected from the nucleus during beta decays.
Beta particles are relatively ionising compared to gamma photons but not as ionising as alpha particles. Beta particles are also moderately penetrating and can pass through paper and very thin metal foils. However, beta particles cannot go through a few millimetres of aluminium.
Beta decay
In beta decay, either an electron or a positron can be produced. The emitted particle allows us to classify the radiation into two types: beta minus decay (β−) and beta plus decay (β+).
1. Beta minus decay
When an electron is emitted, the process is called beta minus decay. It is caused by the disintegration of a neutron into a proton (which stays in the nucleus), an electron, and an antineutrino. As a result, the proton number increases by one, and the nucleon number does not change.
These are the equations for the disintegration of a neutron and beta minus decay:
\[n^0 \rightarrow p^++e^- + \bar{v}\]
\[^{A}_{Z}X \rightarrow ^{A}_{Z+1}Y+e^- +\bar{v}\]
n0 is a neutron, p+ is a proton, e- is an electron, and \(\bar v\) is an antineutrino. This decay explains the change in the atomic and mass numbers of the element X, and the letter Y shows that we now have a different element because the atomic number has increased.
2. Beta plus decay
When a positron is emitted, the process is called beta plus decay. It is caused by the disintegration of a proton into a neutron (which stays in the nucleus), a positron, and a neutrino. As a result, the proton number decreases by one, and the nucleon number does not change.
Here are equations for the disintegration of a proton and beta plus decay:
\[p^+ \rightarrow n^0 +e^+ +v\]
\[^{A}_{Z}X \rightarrow ^{A}_{Z-1}Y + e^+ +v\]
n0 is a neutron, p+ is a proton, e+ is a positron, and ν is a neutrino. This decay explains the change in the atomic and mass numbers of the element X, and the letter Y shows that we now have a different element because the atomic number has decreased.
- A positron is also known as an antielectron. It is the antiparticle of the electron and has a positive charge.
- A neutrino is an extremely small and light particle. It is also known as a fermion.
- An antineutrino is an antiparticle with no electric charge.
Although the study of neutrinos and antineutrinos is out of the scope of this article, it is important to note that these processes are subject to certain conservation laws.
For instance, in beta minus decay, we go from a neutron (zero electric charge) to a proton (+1 electric charge) and an electron (-1 electric charge). The sum of these charges gives us zero, which was the charge we started with. This is a consequence of the law of conservation of charge. The neutrinos and antineutrinos fulfil a similar role with other quantities.
We are concerned about electrons and not neutrinos because electrons are much heavier than neutrinos, and their emission has significant effects and special properties.
Some applications of beta radiation
Like alpha particles, beta particles have a wide range of applications. Their moderate penetrating power and ionisation properties give beta particles a unique set of applications similar to gamma rays.
Beta particles are used for PET scanners. These are positron emission tomography machines that use radioactive tracers to image blood flow and other metabolic processes. Different tracers are used to observe different biological processes.
Beta tracers are also used to investigate the amount of fertiliser reaching different parts of plants. This is done by injecting a small amount of radioisotopic phosphorus into the fertiliser solution.
Beta particles are used to monitor the thickness of metal foils and paper. The number of beta particles reaching a detector on the other side depends on the thickness of the product (the thicker the sheet, the fewer particles that reach the detector).
What is gamma radiation?
Gamma radiation is a form of high energy (high frequency/short wavelength) electromagnetic radiation.
Because gamma radiation consists of photons that have no charge, gamma radiation is not very ionising. It also means that gamma radiation beams are not deflected by magnetic fields. Nevertheless, its penetration is much higher than the penetration of alpha and beta radiation. However, thick concrete or a few centimetres of lead can impede gamma rays.
Gamma radiation contains no massive particles, but, as we discussed for neutrinos, its emission is subject to certain conservation laws. These laws imply that even though no particles with mass are emitted, the composition of the atom is bound to change after emitting photons.
Some applications of gamma radiation
Since gamma radiation has the highest penetrating and lowest ionising power, it has unique applications.
Gamma rays are used to detect leaks in pipework. Similar to PET scanners (where gamma-emitting sources are also used), radioisotopic tracers (radioactive or unstable decaying isotopes) are able to map leaks and damaged areas of pipework.
The process of gamma radiation sterilisation can kill microorganisms, so it serves as an effective means of cleaning medical equipment.
As a form of electromagnetic radiation, gamma rays can be concentrated into beams that can kill cancerous cells. This procedure is known as gamma knife surgery.
Gamma radiation is also useful for astrophysical observation (allowing us to observe sources and areas of space concerning gamma radiation intensity), thickness monitoring in the industry (similar to beta radiation), and changing the visual appearance of precious stones.
Alpha, beta, and gamma radiation are types of nuclear radiation
Alpha, beta, and gamma radiation are types of nuclear radiation, but how was nuclear radiation discovered?
The discovery of nuclear radiation
Marie Curie studied radioactivity (nuclear radiation emission) shortly after another famous scientist named Henri Becquerel discovered spontaneous radioactivity. Curie discovered that uranium and thorium were radioactive through the use of an electrometer that revealed the air around radioactive samples had become charged and conductive.
Marie Curie also coined the term “radioactivity” after discovering polonium and radium. Her contributions in 1903 and 1911 would receive two Nobel prizes. Other influential researchers were Ernest Rutherford and Paul Villard. Rutherford was responsible for the naming and discovery of alpha and beta radiation, and Villard was the one to discover gamma radiation.
Rutherford’s investigation into alpha, beta, and gamma radiation types showed that alpha particles are helium nuclei due to their specific charge.
See our explanation on Rutherford Scattering.
Instruments to measure and detect radiation
There are various ways to investigate, measure, and observe the properties of radiation. Some valuable devices for this are Geiger tubes and cloud chambers.
Geiger tubes can determine how penetrating radiation types are and how absorbent non-radioactive materials are. This can be done by placing various materials of different widths between a radioactive source and a Geiger counter. Geiger-Müller tubes are the detectors used in Geiger counters – the usual device used in radioactive zones and nuclear power plants to determine the intensity of the radiation.
Cloud chambers are devices filled with cold, supersaturated air that can track the paths of alpha and beta particles from a radioactive source. The tracks result from the interaction of the ionising radiation with the material of the cloud chamber, which leaves an ionisation trail. Beta particles leave swirls of disordered trails, and alpha particles leave relatively linear and ordered trails.
Differences between alpha, beta, and gamma radiation
Have you ever wondered what the difference between alpha, beta, and gamma radiation is? And where and how we use each type of radiation in everyday life? Let’s find out!
| Table 1. Differences between alpha, beta and gamma radiation. | ||||
|---|---|---|---|---|
| Type of Radiation | Charge | Mass | Penetration Power | Hazard Level |
| Alpha | Positive (+2) | 4 atomic mass units | Low | High |
| Beta | Negative (-1) | Nearly massless | Moderate | Moderate |
| Gamma | Neutral | No mass | High | Low |
Alpha radiation consists of particles made up of two protons and two neutrons, which gives it a charge of +2 and a mass of 4 atomic mass units. It has a low penetration power, which means that it can be easily stopped by a sheet of paper or the outer layer of skin. However, alpha particles are highly ionizing, meaning that they can cause significant damage to living tissue if they are ingested or inhaled.
Beta radiation consists of electrons or positrons, which gives it a charge of -1 and a nearly non-existent mass. Beta particles have a moderate penetration power, which means that they can be stopped by a few millimeters of aluminum or plastic. Beta radiation is also moderately ionizing, which means that it can cause damage to living tissue if it is not properly shielded.
Gamma radiation consists of high-energy photons, which have no charge and no mass. Gamma rays have a high penetration power, which means that they can pass through many materials, including thick walls and dense metals. Gamma radiation is not highly ionizing, which means that it is less likely to cause direct damage to living tissue. However, it can cause indirect damage by ionizing water molecules in the body and creating harmful free radicals.
In summary, alpha, beta, and gamma radiation have different properties that make them useful for different applications. However, all three types of radiation can be hazardous to human health if they are not properly controlled and shielded.
Effects of alpha, beta, and gamma radiation
Radiation can break chemical bonds, which can lead to the destruction of DNA. Radioactive sources and materials have provided a wide range of uses but can be very damaging if mishandled. However, there are less intense and less dangerous kinds of radiation to which we are exposed every day that do not cause any harm in the short term.
Natural sources of radiation
Radiation occurs every day, and there are many natural sources of radiation, such as sunlight and cosmic rays, which come from outside the Solar System and impact the Earth’s atmosphere penetrating some (or all) of its layers. We can also find other natural sources of radiation in rocks and the soil.
What are the effects of being exposed to radiation?
Particle radiation has the ability to damage cells by damaging DNA, breaking chemical bonds, and altering how the cells work. This impacts how cells replicate and their features when they replicate. It can also induce the growth of tumours. On the other hand, gamma radiation has higher energy and is made of photons, which can produce burns.
Alpha, Beta and Gamma Radiation - Key takeaways
- Alpha and beta radiation are forms of radiation that are produced by particles.
- Photons constitute gamma radiation, which is a form of electromagnetic radiation.
- Alpha, beta, and gamma radiation have different penetrating and ionising capabilities.
- Nuclear radiation has different applications ranging from medical applications to manufacturing processes.
- Marie Curie, a polish scientist and double winner of the Nobel prize, studied radiation after Becquerel discovered the spontaneous phenomenon. Other scientists contributed to discoveries in the field.
- Nuclear radiation can be dangerous depending on its type and intensity because it can interfere with processes in the human body.
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Frequently Asked Questions about Alpha Beta and Gamma Radiation
What are the symbols of alpha, beta, and gamma radiation?
The symbol for alpha radiation is ⍺, the symbol for beta radiation is β, and the symbol for gamma radiation is ɣ.
What is the nature of alpha, beta, and gamma radiation?
Alpha, beta, and gamma radiation are the radiation emitted from nuclei. Alpha and beta radiation are particle radiation, while gamma radiation is a kind of highly energetic electromagnetic radiation.
How are alpha, beta, and gamma radiation different?
Alpha radiation is a highly ionising, low-penetrating particle-like radiation. Beta radiation is an intermediate-ionising, intermediate-penetrating particle-like radiation. Gamma radiation is a low-ionising, highly penetrating wave-like radiation.
How are alpha, beta, and gamma radiation similar?
Alpha, beta, and gamma radiation are produced in nuclear processes but are different in their constituents (particles vs. waves) and their ionising and penetrating powers.
What are the properties of alpha, beta, and gamma radiation?
Alpha and beta radiation are types of radiation made out of particles. Alpha radiation has a high power of ionisation but low penetration. Beta radiation has a low power of ionisation but high penetration. Gamma radiation is a low-ionising, highly penetrating wave-like radiation.
Some atoms are radioactive because their unstable nuclei have too many protons or neutrons, creating a disbalance in the nuclear forces. As a result, these excess subatomic particles are ejected in the form of radioactive decay.
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