Red colour of the sun at the time of sunrise and sunset is because:

The red color of the sun at the time of sunrise and sunset is due to a phenomenon called scattering of light. This phenomenon occurs as sunlight passes through the Earth's atmosphere and interacts with its particles and molecules. The main reason for the red color is that red light is least scattered compared to other colors of the spectrum.

Explanation:

1. Scattering of Light:
- Scattering of light refers to the process of redirection of light by the molecules or particles present in the atmosphere.
- When sunlight passes through the Earth's atmosphere, it encounters various molecules and particles such as oxygen, nitrogen, dust, and water vapor.
- These particles scatter the sunlight in all directions, which is why we see the sky as blue during the day.

2. Rayleigh Scattering:
- The scattering of light in the Earth's atmosphere follows a principle called Rayleigh scattering, named after the British physicist Lord Rayleigh.
- According to Rayleigh scattering, the scattering of light is inversely proportional to the fourth power of the wavelength of the light.
- This means that shorter wavelength light (blue and violet) is scattered more than longer wavelength light (red and orange).

3. Sunrise and Sunset:
- During the sunrise and sunset, the sun is located at a lower angle in the sky, so the sunlight has to pass through a larger portion of the Earth's atmosphere compared to when the sun is directly overhead.
- As the sunlight passes through a longer path in the atmosphere, it undergoes more scattering.
- Since blue and violet light have shorter wavelengths, they are scattered more by the molecules and particles in the atmosphere.
- On the other hand, red and orange light, which have longer wavelengths, are scattered the least.

4. Red Color of the Sun:
- When the sun is close to the horizon during sunrise or sunset, the sunlight has to pass through a thicker layer of the Earth's atmosphere.
- This causes the blue and violet light to be scattered away from our line of sight, while the longer wavelength red and orange light is less scattered and reaches our eyes.
- As a result, the sun appears to be red or orange during these times, creating the beautiful colors that we associate with sunrise and sunset.

Conclusion:

In conclusion, the red color of the sun at the time of sunrise and sunset is due to the phenomenon of scattering of light in the Earth's atmosphere. The longer wavelength red light is scattered the least, while the shorter wavelength blue light is scattered the most. This causes the sun to appear red or orange when it is close to the horizon during sunrise and sunset.