在一个不透明的木板上，钻一个小孔．用眼睛通过小孔可以观察到一定的范围．如图所示．为了扩大观察的范围，在小孔中嵌入各种形状的玻璃制品．则在图中的四个截面中能获得最大观察范围的是（ ）
A．
B．
C．
D．
如图甲，没有任何光学元件，直接通过小孔，看到的范围．
如图乙，小孔内放入玻璃砖，要光线从小孔左侧进入右侧眼睛，经过两次折射，如图光线能进入人的眼睛，人眼看到的范围稍微增大．
如丙图，小孔内放入凸透镜，凸透镜对光线有会聚作用，能使会聚光线提前会聚，要是光线进入人的眼睛，观察到的范围变窄．
如丁图，小孔内放入凹透镜，凹透镜对光线有发散作用，凹透镜使光线错后会聚，要使光线进入人的眼睛，观察到的范围变宽．
乙图和丁图观察范围都变宽，由于玻璃砖两次折射后的光线与原始光线是平行的，要使光线进入人的眼睛，观察到的范围只是稍微增大．凹透镜的发散作用越强，观察到的范围越大．
故选D．
| 完形填空。 | |||
| Welcome 1 the zoo, everyone! Here is our tour plan. 2 carefully. First we will 3 the Children's Zoo. After that, we will walk 4 the Bird World. Next is the 'African Area. 5 are elephants and lions! Don't 6 afraid; the cages are safe. Then, we will have 7 lunch. Everybody brought their lunch, right? Some of you don't have drinks. There are many places 8 drinks. After lunch ,we will go to the Asian Area. Last, there is the Butterfly Park. It's across 9 the Snake Park. Then, we will come back here and get on the bus. Remember, don't feed the animals.OK. Let's 10 ! | |||
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