题干

小明同学在课外用易拉罐做成如图所示的装置做小孔成像实验,如果易拉罐底部有一个很小的三角形小孔,则他在半透明纸上看到的像是(   )

A:蜡烛的正立像

B:蜡烛的倒立像

C:三角形光斑

D:圆形

上一题 下一题 0.0难度 选择题 更新时间:2019-02-18 03:38:07

答案(点此获取答案解析)

B

同类题3

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

    When a New Yorker was hiking in Europe, his Swiss friend kept saying “Listen to that!” but he didn't hear anything. His ears were accustomed to loud city noises and it was days before he was able to notice the sound of a bird. ____. There is background music in restaurants, bars, stores, rest rooms, elevators, and when you are waiting on the telephone. Russell Baker blames “society's determination to entertain you whether you like it or not”.

    ____, but in practice they avoid it. They drive with the car radio turned up, switch on the television when they get home, and exercise while listening to music on headphones. ____ They can buy things in stores, but they do not have enough human contact. So they fill their lives with sound.

    ____. Young men play their car stereos loudly in order to create a personal environment around them. Like animals, they are marking a territory to warn rivals away and to attract a mate.

    It may also be true that the brain itself wants excitement just as the stomach insists on food. ____ This seems extreme. Perhaps we would be better off if we sought periods of silence to provide balance.

A. Sometimes the reason for the noise is primitive

B. The noise suggests that people have a spiritual problem

C. They spend too much time in elevators and the like

D. Unlike in the past, we now have modern technology to supply a constant flood of sounds

E. For most of us, silence has become a rare experience

F. A good response would be to use our brains to improve modern technology

G. People may say they yearn for quiet