第4节 眼睛和眼睛.doc

第4节 眼睛和眼睛
of rural drinking water sources, protection of drinking water sources in rural areas by the end of trces in rural areas by the end of the delimitation of the scope of protection, complete with warning signs, isolating network protection facilities
of rural drinking water sources, protection of drinking water sources in rural areas by the end of the delimitation of the scope of protection, complete with warning signs, isolating network protection facilities
of rural drinking water sources, protection of drinking water sources in rural areas by the end of the delimitation of the scope of protection, complete with warning signs, isolating network protection facilities
实验结论：近视眼患者的晶状体太厚，折光能力太强，导致像成在视网膜的前面。利用凹透镜对光有发散作用来矫正近视眼。
由于近视眼患者的晶状体已经变厚，会使来自远处某点的光会聚在视网膜前，到达视网膜时已经不是一点而是一个模糊的光斑，因此近视眼患者看不到远处的物体。由于凹透镜对光线具有发散作用，佩戴凹透镜制成的近视镜后，射入眼中的光首先会被凹透镜发散，然后再被晶状体会聚，这样就可以使物体的像成在视网膜上。矫正后的示意图如图所示。
1. 近视眼及其矫正
（1）产生原因：晶状体变厚，折光能力变强。
（2）矫正方法：佩戴用凹透镜制成的近视镜。
例1 如图所示，将凸透镜看作是眼睛的晶状体，光屏看作是眼睛的视网膜，烛焰看作是被眼睛观察的物体。拿一副近视眼镜给“眼睛”戴上，光屏上出现的烛焰清晰的像，而拿走近视眼镜则烛焰的像变得模糊。拿走近视眼镜后，为了能在光屏上重新得到清晰的像，下列操作正确的是（ ）
of rural drinking water sources, protection of drinking water sources in rural areas by the end of the delimitation of the scope of protection, complete with warning signs, isolating network protection facilities
of rural drinking water sources, protection of drinking water sources in rural areas by the end of the delimitation of the scope of protection, complete with warning signs, isolating network protection facilities
of rural drinking water sources, protection of drinking water sources in rural areas by the end of the delimitation of the scope of protection, complete with warning signs, isolating network protection facilities




答案：C
解析：近视镜是凹透镜，凹透镜有发散光线的作用,拿走近视镜后，通过凸透镜的光线比以
前会聚得要早了，像距更小了，因此要得到清晰的像，需将光屏靠近凸透镜。
点拨：凹透镜有发散光线的作用,拿走近视镜后，光线比原来变得更加会聚，像成在光屏的前方。
变式训练：
，青少年近视现象十分严重。近视眼在看远处物体时，物体的像落在视网膜的
，（选填“前方”或