The diameter of a sphere is four times the focal length of a concave mirror cut from it.

凹面镜如果是从圆球上切下来的，圆球的直径会是凹面镜焦距的四倍。

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Observation eyepiece consists of concave mirror and a separate gate is formed, in the eyepiece can be seen at the same time the two semicircle color, its left for the sample color.

观察目镜由凹镜和分隔栅组成，在目镜中可同时看到二个半圆色，其左边的为试样颜色。

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Collectively, the faces of all the tiny airborne ice crystals act as a giant concave mirror.

总的来说，所有微小的空中冰晶的面孔扮作一块巨大的凹镜。

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Some old favorites are dusted off and given new life, like a wonderful giant concave mirror that plays tricks on the eyes and the ears.

CNN: San Francisco's Exploratorium opens in sparkling new home