Over those distances, even a sharp laser beam would spread to thousands of kilometres wide by the time it reached Earth.

在这种距离下，即便是聚焦良好的光束到达地球时也会分散到上千公里宽的面积上。

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That, in turn, bounces the light down in a concentrated beam about a metre (3ft) wide to produce heat and drive generators.

这个塔又反过来把光以3米宽的光束集中反射到地上，这样可以产生热量和发电。

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However, if the beam Angle for the direct light is too wide then it will violate the limits of a full cutoff classification.

然而，如果给直接的光光线角度太宽，那么它将会违犯完整近路分类的极限。

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While the patient is still on the operating table, a lead disc is slipped behind the breast tissue to protect the chest cavity, and an eight inch wide electron beam focused directly on the area surrounding the tumour.

BBC: 'One stop shop' for cancer