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gylx1206:几何光学书上有 (2011-12-21 09:51) @&M$`b ^
362429208b:tan汇聚角度=长度一半除以焦距 够通俗了吧 (2011-12-20 17:20) *np%67=jO
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小猫悖悖:长度一半是指透镜的长度吗,还是后焦 (2011-12-23 08:34) QhN5t/Hr