Concept:Twinkling of stars is caused by atmospheric refraction of starlight.
Explanation:Starlight enters Earth’s atmosphere from space.
The atmosphere has layers of air with different optical densities.
Each layer acts as a separate transparent medium.
As starlight travels through these layers, it refracts (bends) repeatedly.
The physical conditions of the atmosphere are not constant.
So the amount of bending changes continuously.
This makes the apparent position of the star fluctuate.
The amount of starlight reaching our eyes varies – sometimes brighter, sometimes fainter.
This rapid change in brightness is the twinkling effect.
Thus, the main cause is atmospheric refraction of starlight.
Answer:B. atmospheric refraction of starlight.
