MCQ Detailed View

Stars seem to twinkle when viewed from Earth, but this is not because their light flickers at the source. The twinkling effect is actually caused by the refraction of light as it passes through the Earth’s atmosphere.

Light from a star travels through space in straight lines. When it enters the Earth’s atmosphere, it passes through different layers of air that have varying temperatures and densities. These layers cause the refractive index of air to change continuously along the light’s path. Because of this, the star's light gets bent multiple times in random directions before reaching our eyes.

As the air in the atmosphere is constantly moving due to winds and temperature fluctuations, the refracted light from the star appears to shift slightly. This rapid change in direction and intensity gives the illusion that the star’s brightness is fluctuating or twinkling.

This phenomenon is more noticeable for stars than for planets. Planets appear larger in the sky, and their light comes from a wider apparent area. Small changes in atmospheric refraction have less effect on them, so they usually shine steadily, whereas stars are point sources of light, making them more affected by turbulence.

Other given options are not responsible for star twinkling:

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  Reflection of light: Occurs when light bounces off a surface; not the cause here.

  
  


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  Polarization of light: Refers to the orientation of light waves, unrelated to twinkling.

  
  


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  Interference of light: Happens when light waves overlap, producing patterns, not twinkling.

  
  

In summary, twinkling of stars is caused by atmospheric refraction, where layers of moving air continuously bend the light path, making stars appear to change brightness and position rapidly when observed from the Earth's surface.