If by mistake some radioactive substance gets inside the human body, then form the point of view of radiation damage, the most harmful will be one which emits

Options

A. `gamma`-rays
B. Neutrons
C. `beta-`particles
D. `alpha-`particle

Explanation

To determine which type of radiation is the most harmful when a radioactive substance enters the human body, we need to analyze the different types of radiation and their effects on biological tissues. Here is a step-by-step solution:

### Step 1: Identify the Types of Radiation
The question provides four types of radiation:
- A) Gamma radiation
- B) Neutron radiation
- C) Beta particles
- D) Alpha particles

### Step 2: Understand the Characteristics of Each Radiation Type
1. **Alpha Particles**:
- Composed of 2 protons and 2 neutrons (helium nucleus).
- Large mass and charge, which means they have a low penetration ability. They can be stopped by a sheet of paper or the outer layer of skin but can cause significant damage if ingested or inhaled.

2. **Beta Particles**:
- Electrons or positrons emitted from a nucleus.
- Smaller mass than alpha particles and can penetrate skin but are less damaging than alpha particles when outside the body.

3. **Gamma Radiation**:
- High-energy electromagnetic radiation with no mass or charge.
- Highly penetrating and can pass through the human body, causing damage to internal organs and tissues.

4. **Neutron Radiation**:
- Consists of neutrons which can also penetrate tissues deeply.
- Neutrons can cause significant biological damage due to their ability to interact with atomic nuclei.

### Step 3: Evaluate the Damage Potential
- **Alpha particles** are very damaging if ingested but are not as harmful externally.
- **Beta particles** can penetrate the skin but are less damaging than alpha particles when ingested.
- **Gamma radiation** has the highest energy and penetration ability, making it extremely harmful to internal tissues.
- **Neutron radiation** is also very damaging due to its ability to cause secondary radiation effects in tissues.

### Step 4: Conclusion
From the perspective of radiation damage when a radioactive substance is ingested, **gamma radiation** is the most harmful due to its high energy and penetrating ability. Therefore, the correct answer is:

**Answer: A) Gamma radiation**