一束光从空气射入某透明介质，入射角为45°，折射角为30°。求该介质对空气的相对折射率。
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Correct answer
A. √2
Principle or equation
折射定律（斯涅尔定律）：n = sin i / sin r，其中 i 为入射角，r 为折射角。
Why this answer is correct
n = sin45° / sin30° = (√2/2) / (1/2) = √2。
Example
若入射角为60°，折射角为30°，则 n = sin60°/sin30° = (√3/2)/(1/2) = √3。
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