如图，是小强用来“研究凸透镜成像规律”的实验装置示意图（光屏_爱下问搜题

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问题问答题

如图，是小强用来“研究凸透镜成像规律”的实验装置示意图（光屏未画出），当蜡烛与透镜放在图示位置时，通过移动光屏，可在光屏上得到与物体等大的像．

（1）若透镜位置不变，将蜡烛移到刻度为30cm处，则______

A．移动光屏，可以在屏上得到倒立、放大的像

B．移动光屏，可以在屏上得到倒立、缩小的像

C．移动光屏，可以在屏上得到正立、放大的像

D．不论光屏移到什么位置，都不能在屏上得到清晰的像

（2）如果利用该透镜和一个小灯泡做一个平行光源，小灯泡应放在透镜前______cm的位置．

答案

（1）由题意可知，此时物距为30cm时，可以在光屏上得到与物体等大的像，所以f=15cm；

将蜡烛移到刻度为30cm处时，物距为10cm，即u＜f，所以应该成正立、放大的虚像，故在光屏上看不到；

故选D．

（2）将小灯泡放在该凸透镜的焦点位置，由小灯泡发出的光线（即过焦点的光线）经过凸透镜折射后，平行于主光轴射出，成为平行光，故小灯泡应放在透镜前15cm处．

故答案为：15cm

阅读理解

选项A－E是下面文章各个段落( 65-68 )的标题，请替下面文章的每个段落找到合适的标题，其中有一个标题是多余的。本节有4小题，每小题1分，共4分。

A. Impoliteness in using electronic communication devices

B. The objection to the use of some devices

C. The annoying noise from the classroom

D. A fact of modern life

E. Disturbance by someone’s screams in public places

小题1:

It’s something that most of us find annoying. We’re on our way home after a hard day at school and trying to have a quiet chat with a classmate or get in a little reading, when our peace is disturbed by someone screaming into their cell phone: “I’M ON THE BUS !”

小题2:

A survey published last week suggests Americans do not like the impolite use of today’s electronic communication gadgets. Besides noisy phone users, sending and receiving e-mails while in company are also as very poor manners, reports MSNBC.com.

小题3: _

One of the practices that participants in the survey most objected to was the use of phones, iPods and other devices during religious festivals. Some 90 per cent of those surveyed thought this was insensitive and disrespectful.

小题4: ___

The survey does suggest, according to MSNBC, that most Americans accepted that the technologies are a fact of modern life. They had nothing against the use of laptops and cell phones in bathrooms. And an electronic thank-you note was just as acceptable as a handwritten one.

问答题

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