A one-way mirror has a reflective coating applied in a very thin, sparse layer — so thin that it's called a half-silvered surface.
单向认人镜具有反光涂层应用于一个非常薄，稀疏的层——如此之薄这被称为一个半镀银的表面。
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The name half-silvered comes from the fact that the reflective molecules coat the glass so sparsely that only about half the molecules needed to make the glass an opaque mirror are applied.