共回答了198个问题采纳率:100%
光屏到凸透镜的距离是20cm,成倒立、缩小的实像,2f>20cm>f,所以凸透镜的焦距是:20cm>f>10cm,所以物体到凸透镜的范围:40cm>u>20cm.
故选D.
点评:
本题考点: 凸透镜成像的应用.
考点点评: 本题根据像距和焦距的关系,求出凸透镜的焦距范围,然后根据物距和焦距的关系进行判断.
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