The pressure of colloidal particles of dust in air imparts blue colour to the sky. This is due to

Options

A. absorption of light by dust particles
B. reflection of light by dust particles
C. scattering of light by dust particles
D. pesence of clouds

Answer

To solve the question regarding why the pressure of colloidal particles of dust in the air imparts a blue color to the sky, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Colloidal Particles**:
- Colloidal particles are small particles that are dispersed in a medium (in this case, air). Dust particles in the atmosphere can be considered as colloidal particles.

2. **Light Interaction with Particles**:
- When light passes through the atmosphere, it interacts with these colloidal particles. The interaction can involve absorption, reflection, or scattering of light.

3. **Scattering of Light**:
- Among the interactions, scattering is a significant phenomenon. When light encounters small particles, it can be scattered in different directions. The amount of scattering depends on the wavelength of the light and the size of the particles.

4. **Rayleigh Scattering**:
- The blue color of the sky is primarily due to Rayleigh scattering, which occurs when the particles are much smaller than the wavelength of light. Shorter wavelengths (blue light) are scattered more than longer wavelengths (red light).

5. **Conclusion**:
- Therefore, the blue color of the sky is a result of the scattering of light by colloidal particles (dust) in the air.

### Final Answer:
The blue color of the sky is due to the scattering of light by dust particles.