Chapter 2: The Human Eye and the Colourful World

Q&A -Ask Doubts and Get Answers

The Human Eye and the Colourful World


Why do stars twinkle?


Stars twinkle in the sky due to atmospheric refraction. The density of air in the atmosphere is not the same everywhere. The density of air is maximum at the earth’s surface and decreases gradually as we move higher. So, the light from the stars undergoes refraction continuously before reaching the earth. As the starlight is travelling from a rarer to a denser atmosphere, it bends the starlight towards the normal and the apparent position of the star is slightly different from its actual position.

 The stars appear slightly higher than its actual position in the sky.

Now, this apparent position of the star is not stationary but keeps on changing slightly due to change in the physical conditions of the earth’s atmosphere due to which different amount of light reaches our eyes. Due to which a star sometimes appears bright and sometimes dim. This causes the twinkling effect of the stars.

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