问题 问答题

在“研究凸透镜成像规律”的实验中:

(1)当蜡烛在凸透镜左侧距透镜20cm时,在右侧光屏上得到一倒立等大的实像,则凸透镜的焦距为______cm;当蜡烛再远离凸透镜5cm时,所成像的性质为______.

(2)小张同学在做实验时,发现光屏上的像在左上角,要使像呈在光屏的中央,若光屏和透镜不动,应将蜡烛向______(左上/右下)调整.

(3)人眼看物体和凸透镜成像原理一样,其中______相当于凸透镜,现在青少年近视现象非常严重,人眼近视是由于像呈现在视网膜的______方,应配戴______(凹/凸)透镜矫正.眼睛是心灵的窗户,我们应该保护好我们的眼睛,为了预防近视你觉得你平时应注意______.

答案

(1)要在屏上成等大、倒立的实像,此时物距必须等于二倍焦距,即2f=20cm,故焦距为10cm,

当蜡烛再远离凸透镜5cm时,此时物距大于二倍焦距,故答案为倒立、缩小的实像;

(2)光屏上的像在左上角,必须向右下方谢调整才到光屏的中心,因此时所成的像是倒立,

所以物体要向相反的方向调整,故答案为左上.

(3)根据眼睛的构造与视物原理,晶状体就相当于一个凸透镜,故答案为晶状体,

而近视的原因,正是因为所成像的位于视网膜的前方,而看不清远处的物体,故答案为前,

凹透镜对光线有发散作用,正好起到矫正目的;

故答案为:凹,保持正确的坐姿才能防止近视.

完形填空

阅读短文,根据要求完成下面各小题。

In a classroom in any countries , the teachers teaches more than art or history or language. He or she teaches something behind---the culture of the country.

In a country such as the United States, people with different history, culture and language join together and the pay much attention to personal ideas. Teachers try to make each student special. Students do not have to remember a lot of information , instead, they work and find answers by themselves. There is often discussion in the classroom..

At an early age students learn to have their own ideas. Their education encourages personal thought.

The importance is placed on how to arrive at an answer and not only to get the correct answer.  

In most Asian countries , people have the same language , history and culture. Perhaps for this reason , the education there pays more attention to group goals than person ideas. Children in China and Japan often work together and help each other on homework. In the classroom, the ways of teaching are often very traditional. The teachers says , and the students listen. There is not much discussion. Instead , the students repeat rules or information that they have been taught in order to keep them in mind .

In many ways these differences come from different educational ideas. In western countries teachers are taught to help students to learn. They make it easier for the students to learn by themselves. In some Asian countries , however , teachers often feel that their job is to pass knowledge to students.

A: 根据短文内容简要回答问题。

小题1: What does the education in the United States encourage ?

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小题2: Which does the education in some Asian countries pay more attention to, group goals or personal ideas?

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B: 将短文中画线的句子译成汉语。

小题3:___________________________________________________________________

小题4: ________________________________________________________________

小题5: 请给短文拟一个恰当的标题。

___________________________________________________

单项选择题