INSIGHT UPSC QUIZ

Science & Technology General Science
Q.

The twinkling of a star occurs due to atmospheric refraction of starlight. This twinkling phenomenon occurs only in stars and not in planets, it is because of which of the following reasons?

Explanation:

 ANSWER: (C)

  • The twinkling of a star is due to atmospheric refraction of starlight. The starlight, on entering the earth’s atmosphere, undergoes refraction continuously before it reaches the earth. 
  • Since the stars are very distant, they approximate point-sized sources of light. As the path of rays of light coming from the star goes on varying slightly, the apparent position of the star fluctuates and the amount of starlight entering the eye flickers – the star sometimes appears brighter, and at some other time, fainter, which is the twinkling effect. 
  • Why don’t the planets twinkle? The planets are much closer to the earth, and are thus seen as extended sources. If we consider a planet as a collection of a large number of point-sized sources of light, the total variation in the amount of light entering our eye from all the individual point-sized sources will average out to zero, thereby ifying the twinkling effect.

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