Stars twinkle in the sky at night because
[amp_mcq option1=”refractive index of the atmosphere changes due to the change of temperature” option2=”stars emit light in the form of pulses” option3=”of interference of light coming from different stars” option4=”of diffraction of light” correct=”option1″]
– Light from distant stars travels through the Earth’s atmosphere before reaching our eyes.
– The atmosphere is not uniform; it consists of layers with varying temperatures and densities.
– Variations in temperature and density cause variations in the refractive index of the air.
– As light from a star passes through these turbulent layers with changing refractive index, it undergoes continuous refraction in random directions.
– This causes fluctuations in the apparent position and brightness of the star as seen from Earth. These rapid fluctuations are perceived as twinkling.
– Planets, being much closer, appear as extended sources of light rather than point sources. The light from different parts of a planet’s disc undergoes similar but independent variations, which average out, so planets do not twinkle noticeably.
Option A correctly identifies the cause: changes in atmospheric refractive index due to temperature variations (and hence density variations) lead to varying refraction of starlight.
Option B is incorrect; stars emit light continuously.
Option C is incorrect; twinkling is an effect on light from a single star due to atmospheric effects, not interference from different stars.
Option D is incorrect; while diffraction occurs, twinkling is primarily an effect of refraction due to atmospheric turbulence.