How Does Gamma Radiation Work in Everyday Life?
Gamma-rays are highly energetic and the most penetrating electromagnetic radiations emitted during the radioactive decay.
These rays were discovered in 1900 by a French chemist and physicist named Paul Villard.
These rays have very short wavelengths and have the highest energy among all the radiations in the electromagnetic spectrum.
These rays are generated by the hottest and the most energetic objects in the universe, such as neutron stars, supernova explosions, pulsars, and regions around black holes.
On Earth, these waves are produced by nuclear explosions, lightning, and the less dramatic activity of radioactive decay.
The specialty of these rays is that they cannot be captured and reflected by mirrors. They have much shorter wavelengths that they can pass through space within the atoms of a detector.
What does Gamma Radiation Mean?
The radioactive nuclei are unstable, and they disintegrate into the daughter nuclei, thereby, emitting α, β, and γ radiations.
γ radiations emitted during the process of gamma decay have very large energy. So what is gamma decay?
Gamma decay is the phenomenon of emission of gamma-ray photons from the radioactive nuclei.
Gamma decay occurs when an excited nucleus shifts itself to a low-energy state. As nuclear states have energies in the order of Mega-electron volt. So, the photons released by the nuclei have very large energies, i.e., in order of MeV; however, their wavelength is much smaller, i.e., < 0.01 ͉Å.
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So, such short wavelength electromagnetic waves emitted by excited nuclei are called γ-rays.
What is Gamma Radiation?
Gamma-rays are highly penetrating electromagnetic radiations emitted by the nucleus of some radionuclides.
The gamma-ray photons emitted during the process of gamma-decay do not have any charge or rest mass.
Therefore, in γ-decay, the daughter nucleus has the same charge number and mass number than that of the parent nucleus.
γ-decay can be expressed as:
zXA → zXA + γ
After the radioactive nuclei undergo α or β-decay, the daughter nucleus is in an excited state and it achieves stability by the emission of one or more γ-ray photons.
For example,
γ-decay of Uranium-235
23892U → 23490Th + 42α
23490Th → 23491Pa + -10β + 00γ (Eγ = 1.17 MeV)
23491Pa → 23492U + -1β + 00γ (Eγ = 1.33 MeV)
Another example,
After the β-decay, the element 27Co60 transforms into an excited 28Ni60 nucleus and then undergoes γ-decay.
The nickel element formed during the reaction reaches the ground state by releasing high-energies as shown in the figure below:
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27Co60 ⇾ 28Ni60** + -1e0
28Ni60** ⇾ 28Ni60* + Eγ (Energy released at this step is 1.1732 MeV).
28Ni60* ⇾ 28Ni60 + Eγ (Energy released when reached to the ground state is 1.3325 MeV).
What are Gamma Rays Used for?
Gamma rays are used in various places, some are outlined below:
In radiotherapy for treating cancer patients.
Soft gamma-rays are used for preserving foodstuff for a long time.
Used in clinics and hospitals for sterilization of medical equipment.
To look for leakages in the pipelines.
In nuclear medicine for diagnoses such as for PET scans and Gamma cameras.
To develop nuclear bombs and nuclear reactors.
Gamma Rays Uses
Various uses of gamma-rays are outlined below:
Gamma rays are used as a disinfectant in industries.
Gamma-ray astronomy: To look for distant objects.
These rays are used by civil engineers to check the density change and the weak points in the oil pipeline.
These rays are used in the measurement and tracking of fluid movements.
Identifying the weld-defects in the materials.
They are used to kill organisms like insects, molds, bacteria, and poisonous food bacteria.
Used in geodesic surveys.
In pasteurization.
Used for resource exploration.
Used for medical imaging and material modification.
In oncology - to kill cancerous cells by focusing these rays into the place where the cells are accumulated.
Proper care is required while operating a cancerous patient because gamma-rays are so powerful that they can damage other organs of the human body.
Gamma Irradiation
Gamma irradiation is used in the field of medicine, which is a physical and chemical means of sterilization.
It kills bacteria deposited on the medical equipment by breaking down bacterial DNA, inhibiting bacterial division.
The energy of gamma-rays is then passed through the equipment, disrupting the pathogens that cause contamination on this equipment.
The gamma-rays are also used to preserve the food through a process called the food irradiation.
In this process, the poisonous bacteria present in the foodstuff are exposed to gamma-rays. In this way, we can preserve our food for a long time.
Here, gamma-rays don't make the food radioactive, it just kills the bacteria present inside them to preserve them for a longer period. However, food irradiation doesn’t kill viruses.
FAQs on Gamma Radiation: Key Concepts, Applications & Precautions
1. What is gamma radiation and what is its symbol?
Gamma radiation (symbolised by the Greek letter γ) is a form of high-energy electromagnetic radiation. Unlike alpha and beta radiation, which consist of particles, gamma rays are pure energy, similar to X-rays but typically with higher energy. They are emitted from the nucleus of a radioisotope during a process called gamma decay, and they travel at the speed of light.
2. How are gamma rays produced?
Gamma rays are primarily produced through three key processes:
Radioactive Decay: They are often emitted from an atomic nucleus immediately following other forms of decay, such as alpha or beta decay. The nucleus is left in an excited, high-energy state and releases a gamma-ray photon to transition to a more stable, lower-energy state.
Nuclear Fission and Fusion: These nuclear reactions, which occur in reactors, bombs, and stars, release enormous amounts of energy, including gamma radiation.
Astronomical Phenomena: Extremely energetic events in space, such as supernovae and the activity around black holes, produce powerful gamma-ray bursts (GRBs).
3. Why are gamma rays considered more penetrating than alpha and beta particles?
The penetrating power of radiation is inversely related to how it interacts with matter. Gamma rays are more penetrating for two main reasons:
No Electric Charge: Unlike alpha particles (which have a +2 charge) and beta particles (a -1 charge), gamma rays are electrically neutral. This means they do not strongly interact with the electric fields of atoms they pass by and are less likely to be deflected or stopped.
No Mass: Being pure energy, gamma rays have no rest mass. They don't collide with atomic nuclei in the same way that particles do. They penetrate materials until they have a chance of interacting with an electron (via Compton scattering or the photoelectric effect) or a nucleus.
4. What is the fundamental difference between gamma rays and X-rays?
While both gamma rays and X-rays are high-energy electromagnetic waves, their fundamental difference lies in their origin, not necessarily their energy. Gamma rays originate from within the atomic nucleus as it transitions from a high-energy state to a lower one. In contrast, X-rays originate from energy changes in electrons outside the nucleus, such as when fast-moving electrons are suddenly decelerated or when electrons drop to a lower energy shell.
5. What are the most important medical applications of gamma radiation?
Gamma radiation is crucial in medicine due to its high energy and penetrating ability. Key applications include:
Cancer Therapy (Radiotherapy): A concentrated beam of gamma rays from a source like Cobalt-60 is aimed at a tumour. The high energy of the rays damages the DNA of cancer cells, destroying them or preventing them from multiplying. This technique is often called 'Gamma Knife' radiosurgery.
Medical Imaging: In procedures like PET (Positron Emission Tomography) scans, a patient is given a radiopharmaceutical that emits positrons. When these annihilate with electrons in the body, they produce gamma rays that are detected to create a 3D image of metabolic activity.
Sterilisation: Gamma rays are used to sterilise medical equipment like syringes, gloves, and implants. Their penetrating power ensures that all microorganisms are killed, even inside packaging, without damaging the equipment with heat.
6. What are some examples of gamma radiation use in industry?
Beyond medicine, gamma rays have several industrial applications:
Industrial Radiography: Similar to an X-ray, gamma rays are used to inspect metal castings, welds, and machine parts for hidden cracks or flaws.
Food Irradiation: Gamma rays can be used to kill bacteria, mould, and insects in food products, extending their shelf life without making the food radioactive.
Gauges and Sensors: They are used in industrial gauges to measure the thickness or density of materials in pipes or on conveyor belts.
7. What materials are effective at shielding against gamma rays?
Due to their high penetrating power, stopping gamma rays requires materials that are very dense and have a high atomic number. The most effective shielding materials are lead (Pb) and, to a lesser extent, thick layers of concrete or steel. The principle is to maximise the probability of a gamma ray interacting with the material. Dense materials pack more atoms into a given space, increasing the chances of absorption or scattering.
8. What are the biological hazards associated with exposure to gamma radiation?
Gamma radiation is an ionising radiation, which means it has enough energy to knock electrons out of atoms and molecules in living tissue. This can lead to:
Cell Damage: It can damage or destroy living cells, leading to radiation sickness (nausea, vomiting) at high doses.
DNA Mutation: By damaging the DNA within cells, gamma exposure can cause genetic mutations, which may lead to cancer or hereditary defects.
Because it can penetrate deep into the body, it can damage internal organs, unlike alpha radiation which is stopped by the skin.
9. How do physical phenomena like the Compton effect help in detecting gamma rays?
Since gamma rays are invisible and have no charge, we cannot detect them directly. Instead, we detect the effects they have on matter. The Compton effect is a key principle used in detectors. In this process, an incoming gamma-ray photon collides with an electron in a detector material (like a scintillation crystal). The photon transfers some of its energy to the electron, causing the electron to be ejected, and the photon itself scatters in a new direction with lower energy. The detector then measures the energy of this ejected electron, which indicates the presence and energy of the original gamma ray.
10. What are the most important safety precautions when working with gamma radiation?
Safety when handling gamma-emitting sources is based on three fundamental principles:
Time: Minimise the duration of exposure. The total dose received is directly proportional to the time spent near the source.
Distance: Maximise the distance from the source. The intensity of radiation decreases with the square of the distance (inverse-square law).
Shielding: Use appropriate absorbing materials, such as thick lead or concrete barriers, between the source and any personnel to block the radiation.
Additionally, personnel often wear dosimeters to monitor their cumulative radiation dose.
