科学素养与生活应用·英语30篇（1）

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为什么彩虹其实是圆形，但我们通常只看到圆弧

A rainbow forms a full circle when sunlight refracts, reflects internally, and exits water droplets at exactly 42 degrees.
Viewers on the ground see only the upper arc because the horizon blocks the lower half of the circle.
From airplanes or mountain peaks, people sometimes witness complete circular rainbows centered on their shadow.
Each observer sees a uniquely positioned rainbow based on their exact location and the sun’s angle behind them.
Red light bends least and appears on the outer edge, while violet bends most and lies innermost in the spectrum.
The circular shape arises from the symmetrical geometry of spherical raindrops interacting with parallel sunlight rays.
No two people ever see the identical rainbow, since each views light reflected from different droplet sets.
Secondary rainbows—fainter and reversed in color order—form from double internal reflections inside droplets.
Meteorologists use rainbow geometry to estimate cloud droplet size and atmospheric humidity levels.
This optical phenomenon demonstrates how everyday weather reveals fundamental principles of light physics.