问题 实验题

显微镜的使用

  (1)当显微镜的镜筒下降时,你的眼睛应注视显微镜的_____________________。

  (2)若在视野左下方看到的是字母d图像,想要把它移到视野的中央,要把玻片往____________移动。由此可知所观察的玻片标本上写的字母应该是_____________。

  (3)观察玻片上字母时,在视野中出现一个污点,转动目镜和移动玻片,污点都没有发生位移,由此可以断定污点最可能在( )

  A.反光镜上      B.目镜上       C.物镜上      D.装片上

  (4)某同学使用的显微镜共有两个目镜、两个物镜,它们有下列四种组合。如果他想在视野中观察到细胞数目最多,应该选择( )

  A.目镜15x,物镜40x             B.目镜15x,物镜10x

  C.目镜5x, 物镜10x             D.目镜5x, 物镜40x

  (5)使用显微镜时,如果光线较暗,应选用反光镜的_______面,用______的光圈。

答案

分析:此题主要考查的显微镜的使用基本技能方面的知识,只有熟练地掌握显微镜的使用操作才能较容易地完成此类题目.

解答:答:(1)当镜筒下降的时候,如果只注视目镜,我们看到不物镜的位置,就容易让物镜压碎了玻片标本,所以在镜筒下降时我们要注视物镜防止其压碎玻片标本.

(2)我们在显微镜下看到的物像是上下左右均颠倒的物像,所以我们移动玻片标本时,标本移动的方向正好与物像移动的方向相反.如我们向右移动玻片标本,而在显微镜内看到的物像则是向左移动的.在题干中物像位于视野中央偏左下方,要想把它移到视野中央,应该向左下方移动玻片标本,物像才向右上方移动移到视野中央,看到的字母是P.

(3)在观察植物细胞时,视野中出现了一个污点,先移动载玻片再转动目镜,污点都没有移动,说明污点不在载玻片和目镜上,那么污点一定在物镜上.

(4)显微镜的放大倍数越大,视野就越小,看到的细胞就越大,但数目最少;显微镜的放大倍数越小,视野就越大,看到的细胞就越小,但数目最多;显微镜的放大倍数的计算是目镜的放大倍数乘以物镜的放大倍数.在四个选项中A选项放大600倍,B选项放大150倍,C选项放大了50倍,D选项放大200倍,只有C选项的放大倍数最小,所以看到的细胞最小数目最多.

(5)显微镜视野亮度的调节:光线强时,用小光圈、平面镜调节;光线弱时,用大光圈、凹面镜调节.如果在光线条件较差实验室里使用显微镜,应该使视野变亮,故用大光圈、凹面镜调节.

故答案为:

阅读理解

English teenagers are to receive compulsory (必修的) cooking lessons in schools. The idea is to encourage healthy eating to fight the country’s increasing obesity (肥胖 )rate. It’s feared that basic cooking and food preparation skills are being lost as parents turn to pre-prepared convenience foods.

Cooking was once regarded as an important part of education in England---even if it was mainly aimed at girls. In recent decades cooking has progressively become a minor activity in schools. In many cases the schools themselves have given up cooking meals in kitchens in the schools. But the rising level of obesity has led to a rethink about the food that children are given and the skills they should be taught.

“What I want is to teach young people how to do basic, simple recipes like a tomato sauce, a bolognaise, a simple curry, a stir-fry---which they can use now at home and then in their later life”, said Ed Balls, the minister responsible for schools.

The new lessons are due to start in September, but some schools without kitchens will be given longer to adapt. There is also likely to be a shortage of teachers with the right skills, since the trend has been to teach food technology rather than practical cooking. Also the compulsory lessons for hands on cooking will only be one hour a week for one term. But the well-known cookery writer, Pru Leith, believes it will be worth it.

“If we’d done this thirty years ago we might not have the crisis we’ve got now about obesity and lack of knowledge about food and so on. Every child should know how to cook, not just so that they’ll be healthy, but because it’s a life skill which is a real pleasure”.

The renewed interest in cooking is primarily a response to the level of obesity in Britain which is among the highest in Europe, and according to government figures half of all Britons will be obese in 25 years if current trends are not stopped.

小题1:The passage mainly talks about        .

A.the reason for obesity

B.the lost cooking skills

C.the healthy eating

D.the compulsory cooking classes小题2:Which of the following is NOT the purpose for English teenagers to receive cooking lessons?

A.To encourage teenagers to eat healthy food.

B.To reduce the country’s increasing obesity rate.

C.To stop parents from turning to pre-prepared convenience foods.

D.To prevent basic cooking and food preparation skills from being lost.小题3:In what way will cooking lessons benefit the students?

A.They will be healthy and enjoy the pleasure of such a life skill as well.

B.They will be able to do some basic, simple recipes like a tomato sauce.

C.They will be able to make food experiments with the knowledge and skills.

D.They will be able to control the level of obesity in the whole country.小题4:The well-known cookery writer, Pru Leith, thinks it        to offer compulsory cooking lessons in schools.

A.difficult

B.necessary

C.funny

D.timely小题5:It can be inferred from the passage that       .

A.cooking has always been an important part of school education in England

B.the obesity rate in Britain has been rapidly growing in recent decades

C.English teenagers will have their cooking lessons twice a week for one year

D.the students will pay a lot of money to the school for the

单项选择题 A1/A2型题