To understand why the clear sky appears blue, we can break down the explanation into several steps:
### Step-by-Step Solution:
1. **Understanding White Light**:
- White light, such as sunlight, is composed of multiple colors, which can be remembered by the acronym "VIBGYOR" (Violet, Indigo, Blue, Green, Yellow, Orange, Red).
- Each color has a different wavelength, with violet having the shortest wavelength and red having the longest.
2. **Scattering of Light**:
- When sunlight enters the Earth's atmosphere, it interacts with air molecules and small particles.
- This interaction causes the light to scatter in different directions. The phenomenon responsible for this scattering is known as Rayleigh scattering.
3. **Rayleigh's Criterion**:
- According to Rayleigh's criterion, the intensity of scattered light is inversely proportional to the fourth power of its wavelength (Intensity ∝ 1/λ^4).
- This means that shorter wavelengths (like violet and blue) scatter much more than longer wavelengths (like red and yellow).
4. **Comparing Wavelengths**:
- Since violet and blue light have shorter wavelengths compared to other colors in the spectrum, they are scattered more effectively in the atmosphere.
- Although violet light scatters even more than blue light, our eyes are more sensitive to blue light, and some of the violet light is absorbed by the ozone layer.
5. **Conclusion**:
- As a result of this scattering, when we look up at the sky during the day, we see a predominance of blue light, which is why the clear sky appears blue.
### Final Answer:
The clear sky appears blue because violet and blue light get scattered more than the lights of all other colors by the atmosphere. Therefore, the correct option is option 3.
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