The apparent flattening of the Sun’s disc at sunrise and sunset is due to atmospheric refraction. As the Sun’s light passes through the Earth’s atmosphere, atmospheric refraction causes the lower portion of the Sun’s disc to appear more flattened compared to the upper part. This distortion is a result of the bending of light near the horizon.
Why does the Sun’s disc appear flattened at sunrise and sunset, and how is this phenomenon related to atmospheric refraction?
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The phenomenon of the Sun’s disc appearing flattened at sunrise and sunset is primarily attributed to atmospheric refraction. Atmospheric refraction is the bending of light as it passes through the Earth’s atmosphere, and it becomes more pronounced near the horizon.
When the Sun is near the horizon during sunrise or sunset, its light has to traverse a longer path through the Earth’s atmosphere compared to when it is directly overhead. The lower portion of the Sun’s disc is more affected by atmospheric refraction, causing it to appear slightly lifted or elevated. This differential refraction creates an apparent flattening of the Sun’s shape.
Additionally, the Earth’s atmosphere acts like a lens, bending the Sun’s rays and causing the lower part of the Sun to be more refracted than the upper part. This unequal refraction further contributes to the flattened appearance of the Sun during these times.
In summary, the Sun’s flattened appearance at sunrise and sunset is a result of atmospheric refraction, where the bending of sunlight near the horizon causes differential refraction across the Sun’s disc, leading to an apparent distortion of its shape.