............. Waves are mainly used in radar.

Options

A. Radio
B. UV
C. X-rays
D. IR

Explanation

To solve the question regarding which type of waves are mainly used in radar, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Purpose of Radar**:
Radar (Radio Detection and Ranging) is a technology that uses waves to detect objects and determine their distance. It is crucial to know what type of waves are suitable for this purpose.

2. **Identify the Characteristics of Radar Waves**:
Radar waves need to have a high wavelength and low frequency. High wavelength allows the waves to travel long distances with minimal loss.

3. **Evaluate the Given Options**:
The options provided are:
- Radio waves
- UV waves
- X-rays
- Infrared waves

4. **Analyze Each Option**:
- **Radio Waves**: These waves have the highest wavelength and the lowest frequency among the given options, making them suitable for radar applications.
- **UV Waves**: These have shorter wavelengths and higher frequencies, which are not suitable for long-distance travel.
- **X-rays**: Similar to UV waves, X-rays have very short wavelengths and high frequencies, making them unsuitable for radar.
- **Infrared Waves**: While they have longer wavelengths than UV and X-rays, they are still shorter than radio waves and are not typically used in radar.

5. **Conclusion**:
Based on the analysis, radio waves are the correct choice as they possess the necessary characteristics (high wavelength and low frequency) for effective radar operation.

### Final Answer:
**Radio waves are mainly used in radar.**

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