Science (086) — AI-generated practice question

A star near the horizon appears to twinkle more vigorously because its light has to travel through a greater thickness of the earth's atmosphere compared to a star overhead. As starlight passes through the atmosphere, it undergoes continuous refraction through layers of varying refractive index. Since atmospheric conditions (temperature, density) keep changing, the path of light varies continuously, causing fluctuations in the amount of light entering the eye. Near the horizon, the longer atmospheric path means greater and more frequent variations, resulting in more vigorous twinkling.

Source: Chapter 10, Section 10.5 – Atmospheric Refraction (Twinkling of Stars)

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• The key idea is path length through the atmosphere: near the horizon = longer path = more layers of varying refractive index = more refraction variation = more twinkling.
• Examiners look for: (1) mention of continuous/variable refraction, (2) the reason why the horizon star is affected more (thicker atmosphere), and (3) the link between fluctuating light and twinkling effect.
• Don't confuse twinkling with scattering — twinkling is purely an atmospheric refraction phenomenon.