Short Answer

Gamma decay is a type of radioactive decay in which an unstable nucleus releases excess energy in the form of gamma rays. These gamma rays are high-energy electromagnetic waves, not particles. In gamma decay, the number of protons and neutrons in the nucleus does not change; only the energy of the nucleus decreases.

Gamma decay usually happens after alpha or beta decay when the daughter nucleus is still in an excited state. The nucleus becomes more stable by emitting gamma radiation. Gamma rays have very high penetrating power and can pass through thick materials.

Detailed Explanation :

Gamma decay

Gamma decay is an important form of radioactive decay in which an unstable atomic nucleus releases energy by emitting gamma rays. These gamma rays are high-frequency and high-energy electromagnetic waves, similar to X-rays but much more powerful. Unlike alpha and beta decay, gamma decay does not involve the emission of particles with mass or charge. Instead, it involves the emission of pure energy from the nucleus.

Atoms can exist in excited energy states just like electrons can. When a nucleus undergoes alpha or beta decay, the daughter nucleus formed often has extra energy trapped inside it. This energy makes the nucleus unstable even though its number of protons and neutrons may be correct. To release this extra energy and reach a stable state, the nucleus emits a gamma ray. This emission is called gamma decay.

Gamma decay is spontaneous and cannot be affected by physical or chemical changes. It occurs because the nucleus seeks the lowest possible energy state.

Nature of gamma rays

Gamma rays are:

• electromagnetic waves
• highly energetic
• chargeless
• massless
• able to travel at the speed of light

Because gamma rays carry a lot of energy, they have the highest penetrating power among all forms of radiation. They can pass through air, paper, plastic, and even thick layers of concrete and lead. This makes them both useful and dangerous.

How gamma decay occurs

Gamma decay occurs after a nucleus undergoes another form of decay, such as alpha or beta decay. These decays leave the nucleus in an excited energy level. Similar to how electrons jump from higher energy levels to lower ones and release photons, the nucleus also jumps to a lower energy state.

The general process is:

Here:

•  is the excited nucleus
•  is the stable nucleus
•  is the gamma ray emitted

Since the number of protons and neutrons does not change, the atomic number and mass number remain the same.

Energy levels in the nucleus

Just like electrons have quantized energy levels around the nucleus, the nucleus itself has quantized energy states. These energy states depend on nuclear structure and interactions. When the nucleus loses energy by emitting a gamma ray, it moves to a lower and more stable state.

The energy carried by the gamma ray corresponds to the difference between these nuclear energy levels. This energy is usually in the range of millions of electron volts (MeV).

Reasons for gamma decay

Gamma decay happens for several reasons:

1. Excess energy after alpha or beta decay
   Most gamma decay follows alpha or beta decay because the daughter nucleus remains in an excited state.
2. Nuclear reactions
   Collisions inside nuclear reactors or particle accelerators can create excited nuclei that release gamma rays.
3. Particle interactions in space
   Cosmic rays and high-energy particles can produce gamma radiation.

Gamma decay vs alpha and beta decay

Gamma decay is different from alpha and beta decay in several important ways:

• No change in atomic number
  Alpha and beta decay change the number of protons; gamma decay does not.
• No change in mass number
  Alpha decay reduces mass; beta decay keeps mass the same; gamma decay does not change it at all.
• Pure energy emission
  Gamma rays are electromagnetic, unlike alpha (helium nucleus) and beta (electron/positron) emissions.
• High penetration
  Gamma rays can pass through thick materials and require strong shielding.

Applications of gamma rays

Gamma decay has many practical applications due to its penetrating power and energy:

1. Medical treatments
   Gamma rays are used in radiotherapy to destroy cancer cells because they kill damaged tissue effectively.
2. Medical imaging
   Gamma cameras and PET scans use gamma-emitting isotopes to create images of organs.
3. Sterilization
   Gamma rays kill bacteria, viruses, and pests, making them useful in sterilizing medical equipment and food.
4. Industrial inspection
   Gamma radiography checks the quality of metal parts and pipelines for cracks.
5. Scientific research
   Gamma rays help study nuclear structure and cosmic events such as supernovas.

Dangers of gamma radiation

Because gamma rays have high energy and deep penetration, they pose serious health risks:

• damage to living cells
• genetic mutations
• increased cancer risk
• radiation sickness

Thickness of lead or concrete is required to block gamma rays. Therefore, proper shielding and safety precautions are essential when handling gamma sources.

Gamma decay in nature

Gamma rays are also produced naturally in:

• radioactive decay chains of uranium and thorium
• nuclear reactions in stars
• cosmic events like gamma-ray bursts
• lightning strikes

This natural gamma radiation contributes to background radiation on Earth.

Conclusion

Gamma decay is the process in which an excited nucleus releases energy in the form of high-energy gamma rays. This decay does not change the number of protons or neutrons but makes the nucleus more stable. Gamma rays are very energetic and have strong penetrating power, making them useful in medicine, industry, and research but also dangerous without proper protection. Gamma decay is an essential concept in nuclear physics and helps explain how nuclei release excess energy.