Why does the sky appear blue on a clear day ?

Explanation

To understand why the sky appears blue on a clear day, we can break down the explanation into several steps:

### Step-by-Step Solution:

1. **Understanding Sunlight**: Sunlight, or white light, is made up of different colors, each with its own wavelength. The colors range from red (longer wavelength) to violet (shorter wavelength).

2. **Interaction with the Atmosphere**: When sunlight enters the Earth's atmosphere, it interacts with air molecules. The atmosphere is composed of various gases, primarily nitrogen and oxygen.

3. **Scattering of Light**: The phenomenon that causes the sky to appear blue is called Rayleigh scattering. This occurs when light waves encounter small particles (like air molecules) in the atmosphere.

4. **Wavelength Dependence**: Rayleigh scattering is more effective at shorter wavelengths. This means that blue light (which has a shorter wavelength) is scattered much more than red light (which has a longer wavelength).

5. **Direction of Scattering**: As sunlight passes through the atmosphere, the blue light is scattered in all directions. This scattered blue light fills the sky and is what we see when we look up.

6. **Perception of Color**: Our eyes are sensitive to this scattered blue light. When we look at the sky, we see the blue light that has been scattered in all directions, making the sky appear blue.

### Final Explanation:
On a clear day, the sky appears blue because the shorter wavelengths of blue light are scattered more than the longer wavelengths by the air molecules in the atmosphere. This scattered blue light reaches our eyes from all directions, giving the sky its characteristic blue color.

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