Gamma Decay

Nature of Gamma Decay

Gamma decay is the emission of gamma rays from an unstable nucleus. These gamma rays are a form of electromagnetic radiation, similar to X-rays but with even higher energy. Unlike alpha or beta decay, gamma decay does not change the atomic number or mass number of the nucleus. Instead, it occurs after alpha or beta decay when the nucleus is left in an excited, unstable state and needs to release excess energy to become more stable.

Because gamma rays are electromagnetic waves, they do not consist of particles like alpha or beta radiation. Instead, they are high-energy photons emitted from the nucleus.

Properties of Gamma Rays

Gamma rays have several important properties:

• They are high-energy photons, meaning they have no mass and no electric charge.
• They have very high penetrating power and can pass through many materials that would stop alpha or beta particles.
• They travel at the speed of light, approximately $3 \times 10^8 \text{ m/s}$.

Because gamma rays have no charge or mass, they are not deflected by electric or magnetic fields.

Effects on the Nucleus

When a nucleus emits gamma radiation, it loses excess energy but does not lose any protons or neutrons. This means:

• The atomic number remains the same.
• The mass number remains the same.
• The nucleus moves from an excited state to a more stable, lower energy state.

Gamma decay often follows alpha or beta decay because these processes can leave the nucleus in an excited state. The emission of gamma rays allows the nucleus to release this extra energy without changing its composition.

For instance, after beta decay, the daughter nucleus may be left with excess energy. It emits a gamma ray to reach a stable state without changing its proton or neutron count.

Uses and Hazards

Gamma rays have many practical uses due to their penetrating power and energy:

• Medical imaging and treatment: Gamma rays are used in cancer treatment (radiotherapy) to kill cancer cells and in medical imaging techniques to view inside the body.
• Sterilisation: Gamma radiation sterilises medical equipment and food by killing bacteria and other pathogens without heating.

However, gamma rays are hazardous because they can penetrate the body and damage living cells, potentially causing radiation sickness or increasing cancer risk. Therefore, strict radiation protection is essential when working with gamma sources. This includes using lead shielding, limiting exposure time, and maintaining distance from the source.