[Physics Class Notes] on Gamma Radiation Pdf for Exam

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.

()

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:

()

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:

1. In radiotherapy for treating cancer patients.

2. Soft gamma-rays are used for preserving foodstuff for a long time.

3. Used in clinics and hospitals for sterilization of medical equipment.

4. To look for leakages in the pipelines.

5. In nuclear medicine for diagnoses such as for PET scans and Gamma cameras.

6. To develop nuclear bombs and nuclear reactors.

Gamma Rays Uses

Various uses of gamma-rays are outlined below:

1. Gamma rays are used as a disinfectant in industries.

2. Gamma-ray astronomy: To look for distant objects.

3. These rays are used by civil engineers to check the density change and the weak points in the oil pipeline.

4. These rays are used in the measurement and tracking of fluid movements.

5. Identifying the weld-defects in the materials.

6. They are used to kill organisms like insects, molds, bacteria, and poisonous food bacteria.

7. Used in geodesic surveys.

8. In pasteurization.

9. Used for resource exploration.

10. Used for medical imaging and material modification.

11. 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 t
his 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.