Asked by Manishjyani67 | 23rd Oct, 2020, 09:00: AM

Expert Answer:

The twinkling of a star is due to atmospheric refraction of star light. The starlight, on entering the earth’s atmosphere,
undergoes refraction continuously before it reaches the earth.The atmospheric refraction occurs in a medium of gradually
changing refractive index. Since the atmosphere bends starlight towards the normal, the apparent position of thestar is
slightly different from its actual position. The star appears slightly higher (above) than its actual position when viewed
near the horizon (refer Figure).
Further, this apparentposition of the star is not stationary, but keeps on changing slightly, since the physical conditions
of the earth’satmosphere are not stationary. 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
star light entering the eye flickers – the star sometimes appears brighter,and at some other time, fainter, which is the twinkling effect.

Answered by Thiyagarajan K | 23rd Oct, 2020, 09:53: AM