Question

Blue colour of the sky is due to

• A. Reflection of light
• B. Refraction of light
• C. Diffraction of light
• D. Scattering of light

Hint:

When considering the blue sky, remember that Rayleigh scattering causes shorter wavelengths like blue to be scattered more than others, making the sky appear blue.

Answer 1

The Correct Option is D

The blue color of the sky is primarily caused by the scattering of sunlight by the Earth's atmosphere. This phenomenon is known as Rayleigh scattering, where shorter wavelengths of light, like blue, are scattered more than longer wavelengths like red. As sunlight passes through the atmosphere, the light is scattered in different directions by air molecules and particles, and the blue light is scattered more because it has a shorter wavelength.
Thus, the correct answer is option (4) Scattering of light.

Answer 2

Step 1: Understand why the sky appears blue.
Sunlight consists of multiple colors, each with different wavelengths. When sunlight enters Earth’s atmosphere, it interacts with the molecules and small particles in the air.

Step 2: Rayleigh scattering principle.
According to Rayleigh scattering, the amount of scattering is inversely proportional to the fourth power of the wavelength. This means:
\[ \text{Scattering} \propto \frac{1}{\lambda^4} \] Shorter wavelengths (like blue and violet) scatter much more than longer wavelengths (like red and yellow).

Step 3: Why blue is seen, not violet.
Although violet light scatters even more than blue, our eyes are more sensitive to blue light and some of the violet light is absorbed by the upper atmosphere. Therefore, we predominantly see the blue color.

Conclusion:
The blue colour of the sky is due to the scattering of light by molecules and small particles in the atmosphere.

Correct Answer: Scattering of light