Media can be divided into optical hydrophobic media and optical dense media.

These two concepts are relative. For example, water is an optically dense medium for air, while air is an optically hydrophobic medium for water.

Then the basic principle of refraction is that when light enters a dense medium from a sparse medium, the light approaches the normal.

However, when light enters the light-sparse medium from the light-dense medium, the light deviates from the normal.

See Baidu Encyclopedia "Refraction of Light" for other supplements.

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