Science (086) — AI-generated practice question

Atmospheric refraction is the refraction of light by the Earth's atmosphere, which has layers of gradually changing refractive index.

Apparent shift near the horizon: As starlight enters the atmosphere, it is continuously refracted (bent towards the normal) through layers of increasing density. This makes the star appear slightly higher than its actual position, especially when viewed near the horizon.

More pronounced near the horizon: Near the horizon, starlight travels a longer path through the atmosphere at a more oblique angle, undergoing greater refraction. Overhead, light travels a shorter, nearly perpendicular path, so refraction is minimal.

Source: Chapter 10, Section 10.5 – Atmospheric Refraction

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• Examiners expect three clear points matching the three parts of the question: definition, mechanism of apparent shift, and reason for horizon effect.
• Key phrase: "gradually changing refractive index" — use it.
• The textbook specifically states the star appears higher than actual when near the horizon — mention this directly.
• Do not mix twinkling with apparent shift; they are different effects in the same section.