问题 问答题

研究凸透镜成像的实验中:

(1)光具座上应放有凸透镜、光屏和蜡烛,______应放在其它两种器材之间;为了使烛焰的像成在光屏的中央,要调整凸透镜和光屏的高度,使它们的中心______.

(2)当光屏上得到一个清晰,缩小的实像时,蜡烛的位置应在透镜的______;若想得到一个清晰放大的实像,蜡烛应向______方向移动.像的大小是逐渐变______;如无论怎样移动光屏都不能接收到蜡烛的像,说明蜡烛处在______的范围了.

(3)利用凸透镜在光屏上已得到蜡烛清晰的像,若此时用黑纸遮住透镜的下半部分,则光屏上的像______

A. 上半部分没有了    B.下半部分没有了      C.像缩小了  D.像变暗了.

答案

(1)探究凸透镜成像实验中,在光具座上依次放置蜡烛、凸透镜、光屏,所以凸透镜在蜡烛和光屏的中间.

蜡烛、凸透镜、光屏,三者在同一条直线上,三者的中心大致在同一高度,像才能呈在光屏的中心.

(2)当光屏上得到一个清晰,缩小的实像时,蜡烛的位置应在透镜的二倍焦距以外;

若想得到一个清晰放大的实像,物距要减小,所以蜡烛应向靠近凸透镜的方向移动.像的大小是逐渐变大;

如无论怎样移动光屏都不能接收到蜡烛的像,说明凸透镜成虚像,所以蜡烛处在一倍焦距的范围了.

(3)遮住凸透镜的下半部,物体上任一点射向凸透镜的上半部,经凸透镜折射后,照样能会聚成像,像的大小不发生变化,折射光线减少,会聚成的像变暗.

故答案为:(1)凸透镜;在同一高度;(2)二倍焦距之外;靠近透镜;大;一倍焦距以内;(3)D.

阅读理解

There is a new type of small advertisement becoming increasingly common in newspaper classified columns.It is sometimes placed among “situations vacant”, although it does not offer anyone a job, and sometimes it appears among “situations wanted”, although it is not placed by someone looking for a job, either.What it does is to offer help in applying for a job.

“Contact us before writing your application”, or “Make use of our long experience in preparing your curriculum vitae or job history”, is how it is usually expressed.The growth and apparent success of such a specialized service is, of course, a reflection on the current high levels of unemployment.It is also an indication of the growing importance of the CV, with the suggestion that it may now qualify as an art form in its own right.

There was a time when job seekers simply wrote letters of application.“Just put down your name, address, age and whether you have passed any exams”, was about the average level of advice offered to young people applying for their first jobs when I left school.The letter was really just for openers, it was explained, everything else could and should be saved for the interview.And in those days of full employment the technique worked.The letter proved that you could write and were available for work.Your eager face and intelligent replies did the rest.

There is no doubt, however, that it is increasing number of applicants with university education at all points in the process of engaging staff that has led to the greater importance of the CV.

小题1:The new type of advertisement which is appearing in newspaper column        

A.informs job hunters of the opportunities available

B.informs employers of the people available for work

C.divides available jobs into various types

D.promises to offer useful advice to those looking for employment小题2:Nowadays a demand for this specialized type of service has been created because          .

A.there are so many people out of work

B.there are so many toplevel jobs available

C.there is a lack of jobs available for artistic people

D.the CV is considered to be a work of art小题3:In the past it was expected that first job hunters would        

A.write an initial letter giving their life history

B.keep any detailed information until they obtained an interview

C.have no qualifications other than being able to read and write

D.pass some exams before applying for a job小题4:The CV has become such an important document because           

A.there has been an increase in the number of applicants with degrees

B.there has been an increase in the number of jobs advertised

C.jobs are becoming much more complicated nowadays

D.the other processes of applying for jobs are more difficult to do

多项选择题