If you focus bright sunlight on dry wood with a glass, it will start burning.
如果你用一块玻璃把强光集中在干木头上，它就会燃烧起来。
He focused the sun's ray on a piece of paper with a burning-glass.
他用一面凸透镜把阳光在纸上聚成焦点。
If you focus bright sunlight on dry wood with a glass, it will start burning.
假如你用镜子将强烈的阳光聚焦于干燥的木头上，它便会燃烧起来。
He focused the sun's ray on a piece of paper with a burning-glass.
他用一面凸透镜把阳光在纸上集成焦点。
He focused the sun's ray on a piece of paper with a burning-glass.
他用一面凸透镜把阳光在纸上集成焦点。
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