Sky appears to be blue in clear atmosphere due to :

Options

A. diffraction
B. dispersion
C. scattering
D. polarization

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks why the sky appears blue in a clear atmosphere.

2. **Identifying the Phenomenon**: The primary reason for the blue color of the sky is **scattering**. Scattering refers to the change in direction of light due to collisions with particles in the atmosphere.

3. **Nature of Light**: White light, which comes from the sun, consists of seven colors (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.

4. **Scattering and Wavelength**: The intensity of scattering is inversely proportional to the fourth power of the wavelength of light. This means that shorter wavelengths (like violet and blue) scatter more than longer wavelengths (like red).

\[ \text{Intensity} \propto \frac{1}{\lambda^4} \]

5. **Comparing Colors**: Since violet, indigo, and blue light have shorter wavelengths, they are scattered more effectively than the other colors.

6. **Resulting Color of the Sky**: Although violet light is scattered the most, our eyes are more sensitive to blue light. Therefore, the combined effect of scattered violet, indigo, and blue light results in the sky appearing predominantly blue.

7. **Conclusion**: The sky appears blue in a clear atmosphere due to the scattering of sunlight by atmospheric particles, with blue light being scattered more than other colors due to its shorter wavelength.