Stars twinkle at night due to:

Correct option is D

The correct answer is (d) atmospheric refraction of starlight.
The phenomenon of star twinkling (also called stellar scintillation) is caused by atmospheric refraction. Here’s a more detailed explanation of how this works and some additional facts:

How Atmospheric Refraction Causes Twinkling:

1. Atmospheric Layers: The Earth's atmosphere is made up of different layers of air with varying temperatures and densities. As starlight travels through the atmosphere, it passes through these layers.
2. Refraction: Refraction is the bending of light as it passes from one medium to another. The change in temperature and density of the air causes the light from a star to bend in different directions.
3. Continuous Bending: Since the atmosphere is not uniform, the light from the star is refracted multiple times in slightly different directions, causing the intensity (brightness) and sometimes even the color of the star’s light to fluctuate rapidly. This fluctuation creates the twinkling effect.