问题 实验题

在探究凸透镜成像的实验中,

⑴王聪同学将凸透镜对着太阳光,调整凸透镜和白纸间的距离,直到太阳光在白纸上会聚成一个最小、最亮的点,如图甲所示,这一操作是为了            

⑵某同学观察到如图乙所示的情况,为得到完整的像,他应将凸透镜向       调节;

甲               乙

答案

(1)测量凸透镜的焦距;(2)下

题目分析:(1)凸透镜正对太阳光时,平行光线平行于主光轴,经凸透镜折射后会聚在主光轴上一点,这点是凸透镜的焦点,测量凸透镜焦点到光心的距离是凸透镜的焦距.如图是为了测量凸透镜的焦距.

(2)如图,像成在光屏的上方,要使像成在光屏的中央,可以使蜡烛向上移动,或把凸透镜向下移动,或把光屏向上移动,因为烛焰、凸透镜、像在一条直线上.

点评:关键是凸透镜成像规律的掌握,知道用第一问方法找出透镜的焦距。

阅读理解

阅读理解。

     When we have small cuts in the skin (皮肤), something strange may happen.The cuts are able to heal

(痊愈) themselves in a couple of days. How does this happen? Read on, and you will find out the secret.

     Every living thing on the earth is made up of cells (细胞). Cells grow and make new cells. Most cells

are very tiny and we can't see them with our eyes. Different cells have different uses. Our skin cells are

special ones.The cells on the surface (表面) of our skin are old dead cells. New skin cells are right under

the surface. These are the living skin cells. They do work for our bodies. They help protect our bodies

and heal cuts. 

     Our bodies make skin cells all the time. As the old cells fall off, new cells grow in the same place. Each

person makes about 18 kg of skin cells during his or her life.Surface skin cells fit together closely with no

gaps between them. When you cut or bum yourself, you can harm your skin cells. A small cut will not do

much harm. Your skin will quickly heal itself by making new skin cells. How do skin cells work? First, the

cells near the cut get bigger and move into the gap. Next, these bigger cells meet in the middle. They form

a new layer (层) of skin cells. Finally, new cells will grow until the gap disappears completely. In this way,

your skin can grow and get well itself.

    How amazing the tiny cells are! Next time you have a cut, don't worry about it.Maybe in a few days, you will be surprised to find it healed.

1. The underlined word "gaps" in the passage means "______" in Chinese. [ ]

A.突起

B.条纹

C.缝隙

2. From the passage, we know that cells ______. [ ]

A.are large and we call see them with our eyes

B.can grow and make new cells

C.aren't in most living things

3. Skin cells heal cuts in three steps.______ is the right order. 

      

                 a                         b                         c[ ]

A.a→b→c

B.b→c→a

C.a→c→b

4. Which of the following is TRUE according to the passage? [ ]

A.Each person can make 18 kg of skin cells every day.

B.Different cells have different uses in our bodies.

C.The skin cells have little work to do in the body.

5. The best title for this passage should be ______. [ ]

A.HOW SKIN CELLS HEAL CUTS

B.THE IMPORTANCE OF SKIN

C.HOW TO PROTECT OUR FINGERS

多项选择题