问题 问答题

如图所示,水平地面上有一障碍物ABCD,较大平面镜MN在某一高度水平放置,试用作图法求出眼睛位于O点从平面镜中所能看到的障碍物后方地面的范围.如果想在原处看到更大范围的地面,水平放置的镜子的高度应______.

答案

①根据光路的可逆性,将O点看成是一个发光点.作O点在平面镜中的像O′,连接OA交MN于F,连接O′F交地面于H;连接O′B交MN于E,交地面于G,连接OE,标上箭头,光线传播方向如图所示.

入射光线为HF、GE;反射光线为FO、EO.图中GH所围区域就是眼睛位于O点从平面镜MN中所能看到障碍物后方地面的范围.

②假定水平放置的镜子的高度降低至与障碍AB面接触,眼睛就看不到障碍物后面的地面,因此,如果想在原处看到更大范围的地面,水平放置的镜子在高度该增高(即向上移动).

故答案为:见上图;向上移动.

完形填空

阅读下面的短文并回答问题,然后将答案写到相应的位置上(请注意问题后的词数要求)。

[1]E-mail may be the most important, unique method for communicating and developing relationships since the telephone.First of all, ____________.Anyone who can use a word processor can also write an e-mail message without difficulty.Secondly, it saves time and money.It costs nothing more than your time.No paper expense, no postage and no envelope expense.People also find it familiar and safe because it is similar in many respects to writing letters but avoids the annoyances of addressing envelopes, licking stamps, and trips to the mailbox.

[2] Of all the methods for developing relationships on the Internet, e-mail is the most common and perhaps the most powerful.Although friendships and romances may indeed begin in chat rooms, instant messages, blogs, or other online tools improve greatly by becoming more effectively visual and auditory(听觉的), as in video teleconferencing, e-mail will not disappear.Many people will prefer it because it is a non-visual and non-auditory form of communication.After all, we don’t see people rushing out to buy video equipment to add it to their telephone.

[3] E-mail is not just an electronic mail sent via the Internet.It creates a psychological space in which pairs of people or groups of people communicate with each other.It creates a situation in which human relationships can be unfolded.

小题1:What is the main idea of the text? (no more than 12 words)

                                                                           

小题2:Complete the following statement with words from Paragraph 2.(no more than 4 words )After people begin their relationship in chat room, e-mail plays the role of being a way to        

                                                                           

小题3:Fill in the blank in Paragraph 1 with proper words.(no more than 6 words )

                                                                           

小题4:What situation can the E-mail create? (no more than 9 words )

                                                                           

小题5:What does the underlined word “ it ” (Paragraph 2) probably refer to ? (no more than 3 words )

                                                                           

单项选择题