What causes the apparent twinkling of stars when viewed from the surface of the Earth?
Answer and explanation
Correct answer: B. Atmospheric refraction of starlight through turbulent air layers of varying optical density
- Step 1: Starlight enters Earth's atmosphere and undergoes continuous refraction through layers of air whose temperature and density vary constantly.
- Step 2: This shifts the apparent position of the star and the quantity of light entering the pupil, producing the twinkling effect.
Answer
Atmospheric refraction of starlight through turbulent air layers of varying optical density.
Why not the others: Stars emit light steadily on human timescales; interstellar scattering causes reddening rather than rapid twinkling; and reflection from ice crystals creates optical halos.
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