Non-ionising radiations damaging to DNA are

Options

A. X-rays
B. U.V. rays
C. Gamma rays
D. Beta rays

Answer

### Step-by-Step Solution

1. **Understanding Non-Ionizing Radiation**:
Non-ionizing radiation refers to electromagnetic waves that do not carry enough energy to ionize atoms or molecules. This includes types of radiation such as radio waves, microwaves, infrared, and ultraviolet (UV) rays.

2. **Identifying Types of Radiation**:
The question lists several types of radiation: X-rays, UV rays, gamma rays, and beta rays. Among these, X-rays, gamma rays, and beta rays are considered ionizing radiation because they have enough energy to remove tightly bound electrons from atoms, thus causing ionization.

3. **Focusing on UV Rays**:
Ultraviolet (UV) rays are a type of non-ionizing radiation. They have higher energy than visible light but are not as energetic as X-rays or gamma rays. UV rays are known to be harmful to living organisms.

4. **Mechanism of Damage**:
UV rays can damage DNA by causing the formation of thymine dimers, which are covalent linkages between adjacent thymine bases in DNA. This can lead to mutations and disrupt normal cellular processes.

5. **Consequences of UV Damage**:
The damage caused by UV rays can result in various health issues, including skin aging, skin cancers, and eye conditions such as cataracts and snow blindness due to corneal inflammation.

6. **Conclusion**:
Therefore, the non-ionizing radiation that is damaging to DNA is primarily UV rays.

### Final Answer:
**The non-ionizing radiation that damages DNA is UV rays.**

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