假设视网膜为一个平面,光在空气中不折射,眼球的成像原理为小孔成像. 思考如下成像原理: 如图,地面内有圆
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, 其圆心在线段
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上,且与线段
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交于不与
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重合的点
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,
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地面,且
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,
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点为人眼所在处,视网膜平面与直线
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垂直. 过
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点作平面
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平行于视网膜平面. 科学家已经证明,这种情况下圆
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上任意一点到
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点的直线与平面
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交点的轨迹(令为曲线
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)为椭圆或圆,且由于小孔成像,曲线
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与圆
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在视网膜平面上的影像是相似的,则当视网膜平面上的圆
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的影像为圆时,圆
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的半径
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为
. 当圆
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的半径
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满足
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时,视网膜平面上的圆
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的影像的离心率的取值范围为
.
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