问题 问答题

某同学利用焦距为12cm的凸透镜做成像实验,得到的数据记录如下:

实验次数物距u/cm像距v/cm凸透镜的放大率β
130200.7
224241
318362
415604
(凸透镜的放大率β=
烛焰像的大小
烛焰的大小

(1)从表中的数据可以得到u、v、β关系是β=______;

(2)使用照相机拍近处物体的特写镜头时,应该将照相机的镜头______(选填“伸长”或“缩短”);

(3)若底片上物体的像的位置偏上,为了使像成在底片中央,应当将镜头向______(选填“上”、“下”、“左”或“右”)移动.

答案

(1)从表中的数据可知,凸透镜的放大率β=0.7=

20cm
30cm
、β=1=
24cm
24cm
、β=2=
36cm
18cm
…由此可得u、v、β三者关系是:β=
v
u

故答案为:

v
u

(2)使用照相机拍近处物体的特写镜头时,物距变小,照相机所成的像变大了,像距也要变大,镜头到底片的距离变大,所以应该将照相机的镜头伸长一些.

故答案为:伸长.

(3)因为因照相机成像时,在底片上的像是倒立缩小的实像,与物体是上下颠倒的,所以若底片上物体的像的位置偏上,为了使像成在底片中央,应当将镜头向下移动.

故答案为:下.

单项选择题
阅读理解

Japanese students work very hard but many are unhappy.They feel heavy pressures from their parents to do well in school.Most students are always being told by their parents to study harder so that they can have a wonderful life.Though this may be good ideas for those very bright students,it can have very bad results for many students who are not quick enough at learning.

Unfortunately,a number of students killed themselves.Others are after comfort in using drugs.Some do bad things with trouble-makers and turn to crime.Many of them have tried very hard at school but have failed in the exams and have disappointed their parents.Such students feel that they are less important and leave school before they have finished their study.

It is surprising that though most Japanese parents are worried about their children, they do not help them in any way.Many parents feel that they are not able to help their children and that it is the teachers' work to help their children.To make matters worse, a lot of parents send their children to special school called juku-cram schools.These schools are open during the evening and on weekends, and their only purpose is to prepare students to pass exams, they do not try to educate students in any real sense of the real world. It thus comes as a shock to realize that almost three quarters of the junior or high school population attend these cram schools.     

Ordinary Japanese schools usually have rules about everything from the students' hair to their clothes and things in their school bag.Child psychologists now think that such strict rules often lead to a feeling of being unsafe and being unable to fit into society.They regard the rules as being harmful to the development of each student.They believe that no sense of moral values is developed and that students are given neither guidance nor training in becoming good citizens.

小题1:A lot of Japanese students are unhappy at school because                

A.they work very hard

B.they find they can't do well at school

C.they feel unimportant

D.they are under too much pressure小题2:Because of their failure at school, some students take drugs to          

A.kill themselves

B.seek comfort

C.disappoint their parents

D.make trouble小题3:What should be the best title of the passage?

A.Students' Pressure

B.Students' Problems     

C.The Negative Impact(影响) of Japanese Education     

D.The Trouble in Japanese Schools小题4:In juku-cram schools students              

A.are taken good care of by the teachers

B.feel no pressure

C.are trained to pass exams

D.can learn a lot of useful things小题5:In ordinary Japanese schools,       .

A.there are strict rules

B.students feel safe     

C.students can do anything

D.learning is not important