全国爱眼日是每年的6月6日，2013年世界爱眼日主题确定为“关爱青少年眼健康”，某中学为了解该校学生的视力情况，采用抽样

How to Protect Our Eyes
We can't do anything without eyes in our daily lives. We use them to read to books, to watch/watching TV….We can't do at any time and any place. If we have bright eyes, we can be able to see clear beautiful flowers, pretty grass, elegant mountains, graceful rivers and any other landscapes.
However, we do not notice sanitation of using eyes specially in our childhood. If we become near-sighted, it is very difficult to see these beautiful things. So protecting our eyes is very important.
How to protect our eyes? At first, we should not use eyes for a long time. Second, we should keep a distance of one foot when (we are)reading books. Third, don’t read under sun or in the dark light or when we are on a bus or in bed. At last, insist doing health care eyes very day. If we can do the above, we can have bright eyes.

晶状体　不在强光下看书，不长时间近距离看书……（第二、三空为开放性试题，回答正确即可）

人能看清远近不同的物体，是由于睫状体对晶状体的调节作用，当睫状体舒张时，晶状体的曲度变小，使人看清远处的物体；反之，则能看清近处的物体。当睫状体持续收缩时，无法正常调节晶状体的曲度，就会形成近视眼。

Today is the National Eyes Caring Day,so I remind everybody to treasure your eys.Now let me introduce something should be remembered to treasure our eyes especially to the stdents.
First of all,it's important to keep the standard sitting position while you are reading and studying which means that you can't put your eyes to close to the books or notebooks.Secondly,you should keep on doing eye exercises during the ten-minute break carefully.Thirdly,try to look far into the distance during the break,too.Besides,you should remember that if there is something wrong with your eyes,go to see the doctor in time.I believe that if you do as what I say,you can keep on owning good eyesight.
希望能帮上你喔!

解题思路：要解答本题需掌握：①人眼的晶状体相当于凸透镜，物体到晶状体的距离大于2倍焦距成倒立、缩小的实像；
②正常人眼的明视距离是25厘米；
③近视眼是因为人眼的晶状体曲度变大，像呈在视网膜的前方，晶状体曲度越大，像离视网膜越远，因此矫正时所配眼镜的“度数”越大．
④根据凹透镜对光线的发散作用可知，配戴凹透镜可矫正近视眼．

（1）正常人眼的明视距离是25厘米，25厘米时人眼看的物体最清晰，所以读写时，眼睛与书本的距离应保持25cm．
故答案为：25．
（2）近视眼是因为人眼的晶状体曲度变大，会聚能力增强，像呈在视网膜的前方，矫正近视眼，应佩戴发散透镜，即凹透镜，使光线推迟会聚，晶状体曲度越大，像离视网膜越远，因此矫正时所配眼镜的“度数”越大．
故答案为：凹；大．

点评：
本题考点： 近视眼的成因与矫正办法．

考点点评： 此题主要考查学生对近视眼的成因以及矫正方法的理解和掌握，利用凹透镜对光线的发散作用，可佩戴凹透镜进行矫正，关键还是要养成良好的读数、写字习惯，还要注意用眼卫生等，这些都是预防眼睛产生这种病变的措施．
此题与我们的实际生活联系密切，体现了生活处处皆物理的思想．

解题思路：（1）由频数直方图可知：本次调查共抽测的学生人数为各组频数之和，相加可得答案；
（2）由题意可知：在这个问题中，样本指的是160名学生的视力情况；根据公式：频率=频数÷总人数得：相比可得视力在第四组内的频率；
（3）从图中可以看出：160名学生中视力不良的人数，及占总人数的频率，根据用样本估计总体可估计全校2000名学生中视力不良的人数．

（1）由频数直方图可知：本次调查共抽测的学生人数为10+30+60+40+20=160人；

（2）由题意可知：在这个问题中，样本指的是160名学生的视力情况．根据公式：频率=频数÷总人数得：视力在第四组内的频率=40÷160=0.25；

（3）从图中可以看出：160名学生中视力不良的人数为10+30+60=100人，占总人数的频率为100÷160=0.625，则全校2000名学生中视力不良的人数为2000×0.625=1250人．
故答案为（1）160；（2）160名学生的视力情况0.25；（3）1250人．

点评：
本题考点： 频数（率）分布直方图；用样本估计总体．

考点点评： 本题考查读频数分布直方图的能力和利用统计图获取信息的能力．利用统计图获取信息时，必须认真观察、分析、研究统计图，才能作出正确的判断和解决问题．

解题思路：①人眼的晶状体和角膜相当于凸透镜，视网膜相当于光屏，外界物体在视网膜上成倒立、缩小的实像；②近视眼的晶状体较厚，会聚能力较强，看远处的物体时，将像成在视网膜的前面，需戴凹透镜矫正．

人眼球对光的作用相当于凸透镜，远处物体在正常人眼球视网膜上所成的像是倒立、缩小的实像，
近视眼是由于晶状体对光线的会聚作用太强，使像成在视网膜的前方，由图可以看出，这是近视眼的成像光路图，为了使像成在视网膜上，就要戴凹透镜来矫正．
故答案为：凹．

点评：
本题考点： 近视眼的成因与矫正办法．

考点点评： 本题考查了眼睛的成像原理和近视眼的成因．近视眼是由于像成在了视网膜的前方，近视要用凹透镜来矫正．

（1）晶状体  （2）不会  （3）耳  神经  条件
（4）不要在暗弱光线下和直射的阳光下看书写字

由图可知，物体的像成在了视网膜的前方，是近视眼，需要佩戴凹透镜进行矫正；
为了保护视力保护视力不要在光线太强或太暗的地方读书写字．
故答案为：凹；不要在光线太强或太暗的地方读书写字（答案不唯一）．

（1）正常人眼的明视距离是25厘米，25厘米时人眼看的物体最清晰，所以读写时，眼睛与书本的距离应保持25cm．
故答案为：25．
（2）近视眼是因为人眼的晶状体曲度变大，会聚能力增强，像呈在视网膜的前方，矫正近视眼，应佩戴发散透镜，即凹透镜，使光线推迟会聚，晶状体曲度越大，像离视网膜越远，因此矫正时所配眼镜的“度数”越大．
故答案为：凹；大．

预防近视要做到：三要、五不看、三个一，有效地预防了近视眼的发生．
三要是：读书写字的姿势要正确；看书写字40分钟后要到室外活动或向远处眺望一会儿；要认真做眼保健操，所按穴位要准确．
五不看是：不要在暗弱光线下和直射的阳光下看书写字；不要躺在床上、在公共汽车上或走路时看书；不要看字体过小、字行过密、字迹印刷不清的读物；做作业不要用淡色铅笔；看电视时间不要太久．
三个一是：一尺、一拳、一寸，即读书写字时，眼睛和桌面要保持一尺的距离；身体和课桌之间保持一个小拳头的间隔；握笔时手和笔尖要保持一寸的距离．
总之，预防近视要养成良好的用眼习惯．
故答案为：
①三要是：读书写字的姿势要正确；看书写字40分钟后要到室外活动或向远处眺望一会儿；要认真做眼保健操，所按穴位要准确．
②五不看是：不要在暗弱光线下和直射的阳光下看书写字；不要躺在床上、在公共汽车上或走路时看书；不要看字体过小、字行过密、字迹印刷不清的读物；做作业不要用淡色铅笔；看电视时间不要太久．

（1）晶状体太厚，折光能力太强；
（2）不在强光下看书，经常做眼保健操等。

略

National Eye DayToday, young people myopia has become hot issue of society, "focus on prevention, but we must be concerned about students who have myopia." In this regard, the implementation of visual health intervention shijiazhuang works to prevent change by intervention, by the passive change initiative, open the " bright, "the first of its kind, the first time the concept of health interventions in order to comprehensively promote the quality of the educational concept of love to wake up the whole society's awareness of eye protectors." Shijiazhuang City elementary and middle school students with visual health intervention project "to start in September last year, it has been free More than 170,000 primary and middle school students for the creation of the "optometrists files", and distributed vision health card. With this health card, students can at any time to the Health Education Bureau eyesight testing and counseling, all information will also be write "student optometrists files" These files are all stored in the Department of Education's Student Health care, the optometrists will follow students to leave the files until graduation. so that "glasses" spectacles care is already形势所迫, the general trend and deserves our attention implemented as soon as possible

National Eyes Caring Day
National Eye Health Day

How to Protect Our Eyes
Eye is the window of our mind. We use our eyes to see everything around us. Without
eyes, nothing is left beside you but darkness.
How to protect our eyes? It's not right to keep your eyes working for a long time.
You'd better not read in a strong or poor light. Don't read in bed or on a moving bus.
Remember to keep your books away from your eyes for about a foot and do eye-exercises
every day. What's more, a balanced diet is necessary.
Follow my advice and form a good habit. It's time to say goodbye to thick glasses.
答案不唯一

解题思路：（1）近视眼成因：眼球晶状体的曲度过大，远处物体反射来的光线通过晶状体折射后形成的物像，就会落在视网膜的前方造成近视眼．
（2）眼睛是我们心灵的窗户，它是一个相当复杂的天然光学仪器，不断把五彩缤纷的世界告诉我们，我们每个同学都要爱护自己的眼睛．

（1）晶状体和角膜的共同作用相当于一个凸透镜，它把来自物体的光会聚在视网膜上，形成物体的像．
而近视眼的成因是只能看清近处的物体，看不清远处的物体，产生近视眼的原因是：晶状体太厚，折光能力太强，或者眼球在前后方向上太长，因此来自远处点的光会聚在视网膜前，对近视眼的矫正可通过凹透镜对光线的发散作用进行矫正．
（2）眼睛是我们心灵的窗户，为了爱护自己的眼睛，不在强光下看书，走路时不要看书，经常做眼保健操等．
故答案为：（1）晶状体太厚，折光能力太强；（2）不在强光下看书，经常做眼保健操等．

点评：
本题考点： 近视眼的成因与矫正办法．

考点点评： 本题主要考查了眼睛及其视物原理与近视眼的成因．属于识记性内容，比较简单．

How to Protect Our Eyes
Eye is the window of our mind.We use our eyes to see everything around us.Without eyes,nothing is
left beside you but darkness.
How to protect our eyes?It's not right to keep your eyes working for a long time.You'd better not read
in a strong or poor light.Don't read in bed or on a moving bus.Remember to keep your books away from
your eyes for about a foot and do eye-exercises every day.What's more,a balanced diet is necessary.
Follow my advice and form a good habit.It's time to say goodbye to thick glasses.
(答案不唯一)

June 6 of every year is the National Eyes Caring Day. The topic of the day is to protect your own eyes.It is important for senior students to care their eyes.It is unconvienent for life and study if you have a bad eyesight.We suggest that all of the classmates get a good habit of using eyes to protect our eyes.

解题思路：解答本题需掌握：近视眼是晶状体会聚能力增强，像成在视网膜的前方，应佩戴凹透镜矫正．

正常眼睛的明视距离是25cm，而近视眼会由于聚光能量增强，像成在视网膜的前方，
因此患了近视眼的同学应该戴一个凹透镜．
故答案为：凹．

点评：
本题考点： 近视眼的成因与矫正办法．

考点点评： 本题主要考查学生对近视眼的成因以及矫正方法的理解和掌握，是一道基础题，也是中考的热点．