问题 填空题

某同学在普通光学显微镜下观察洋葱鳞片叶的表皮细胞时,显微镜的目镜是10×,物镜为10×,这时观察到的物像比实际大小放大了______倍.若此时观察到的物像位于视野的左上方,则应向______方移动装片,物像才能被移到视野中央.

答案

显微镜是用来观察肉眼看不到的物体的一种仪器,显微镜的放大倍数是目镜和物镜放大倍数的乘积.某同学用显微镜观察植物细胞时,选择了10倍的目镜和10倍的物镜,他看到的细胞被放大了10×10=100倍.因为从目镜内看到的物像是倒像,物像移动的方向与标本移动的方向相反,向右移动玻片,物像就会向左移动,所以,要想把物像移到视野中央,应该是物像往哪偏,标本就应该往哪移,这样物像才能移到视野中央.如果一个物像位于视野的左上方,为了使物象移动到视野中间,应该使玻片向左上方移动,这样物像会向右下方移动,才能移动到视野的中央.

故答案为:100;左上

选择题
阅读理解

阅读理解。

     Many teenagers feel that the most important people in their lives are their friends. They believe that their

family members don't know them as well as their friends do. In large families, it is quite often for brothers

and sisters to fight with each other and then they can only go to their friends for some ideas. 

     It is very important for teenagers to have one good friend or a group of friends. Even when they are not

with their friends, they usually spend a lot of time talking among them on the phone. This communication is

very important in children's growing up, because friends can discuss something. These things are difficult

to say to their family members.

     However, parents often try to choose their children's friends for them. Some parents even stop their

children from meeting their good friends. Have you ever thought of the following questions?

     Who chooses your friends? Do you choose your friends or your friends choose you? Have you got a

good friend your parents don't like? Your answers are welcome.

1. Many teenagers think that _____ can understand them better. [ ]

A. friends

B. brothers

C. sisters

D. parents

2. _____ is very important to teenagers. [ ]

A. To make friends

B. Communication

C. To stop meeting friends

D. Both A and B

3. When teenagers have something difficult to say to their parents, they usually _____. [ ]

A. stay alone at home

B. fight with their parents

C. discuss it with their friends

D. go to their brothers and sisters for help

4. The sentence "Your answers are welcome" means "_____". [ ]

A. You are welcome to discuss the questions with us

B. We've got no idea, so your answers are welcome

C. Your answers are always right

D. Your can give us all the right answers

5. Which of the following is the writer's attitude?[ ]

A. Parents should choose friends for their children.

B. Children should choose everything they like.

C. Parents should understand their children better.

D. Teenagers should only go to their friends for help.