.......... rays do not scatter easily in fog.

Options

A. Ultraviolet
B. Infrared
C. Red
D. Green

Explanation

To solve the question, ".......... rays do not scatter easily in fog," we need to identify which type of rays are least likely to scatter in fog. We have the options: ultraviolet, infrared, red, and green.

### Step-by-Step Solution:

1. **Understanding Scattering**:
- Scattering occurs when light interacts with particles in the atmosphere, such as water droplets in fog. The extent of scattering depends on the wavelength of the light.

2. **Wavelength and Frequency Relationship**:
- The electromagnetic spectrum shows that as we move from gamma rays to radio waves, the frequency decreases while the wavelength increases.
- Rays with longer wavelengths tend to scatter less than those with shorter wavelengths.

3. **Analyzing the Options**:
- **Ultraviolet Rays**: These have a shorter wavelength and higher frequency. They scatter more easily.
- **Infrared Rays**: These have a longer wavelength and lower frequency, making them less likely to scatter.
- **Red Rays**: These are part of the visible spectrum and have a longer wavelength than ultraviolet but shorter than infrared.
- **Green Rays**: These are also part of the visible spectrum and have a medium wavelength, which means they can scatter more than infrared.

4. **Conclusion**:
- Among the given options, infrared rays have the longest wavelength and the lowest frequency, which means they do not scatter easily in fog. Therefore, the correct answer to fill in the blank is **infrared**.

### Final Answer:
Infrared rays do not scatter easily in fog.

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