Question

The stars twinkle in the night because
A. They emit light intermittently
B. The star’s atmosphere absorb light intermittently
C. The earth’s atmosphere absorb light intermittently
D. The refractive index of the air in atmosphere fluctuates

Answer 1

Hint: We need to know the concept of atmosphere refraction. Atmosphere refraction is the deviation or bending of light that takes place in the atmosphere due to variation density levels.

Complete step by step solution:
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. The atmospheric refraction occurs in a medium of gradually changing refractive index.
Since the atmosphere bends starlight towards the normal, the apparent position of the star is slightly different from its actual position. The star appears slightly different from its actual position.

Since the physical conditions of the earth’s atmosphere are not stationary. The stars are very distant, they approximately 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 – the star sometimes appears brighter and fainter, which is a twinkling effect.

Hence the correct answer is option (d)

Note: The stars don’t really twinkle, they just appear to twinkle when seen from the surface of earth. The stars twinkle in the sky because of the effects of different density in the atmosphere. This causes the light from the star to twinkle when seen from ground.