小明用凸透镜、蜡烛、光屏和刻度尺等器材,探究凸透镜成像的规律。 (1)如图所示,

题型:探究题

问题:

小明用凸透镜、蜡烛、光屏和刻度尺等器材,探究凸透镜成像的规律。 

(1)如图所示,将凸透镜正对着太阳光,把光屏置于另一侧,改变光屏与凸透镜间的距离,直到光屏上出现一个 ________ 的光斑,测得凸透镜的焦距是 _________ cm。

(2)小明将蜡烛、凸透镜和光屏的中心调到同一高度,无论怎样移动光屏,都不能得到清晰的像原因可能是 _______________。

(3)实验一段时间蜡烛变短,要使烛焰像仍然成在光屏的中心,应将光屏向 ________ 移动。

考点:凸透镜成像的规律焦点,焦距
题型:探究题

Long, long ago there was an old man. He had a very big orange tree in his garden. On the tree there were many fine oranges.

One day the old man found one of the oranges was bigger than the others. It was as big as a watermelon. So he took the big orange to the king. The king was very happy and gave the old man a lot of money for it.

When a rich man heard of this, he said to himself, "It is only an orange. Why did the king give him so much money? If I take my gold cup to the king, he will give me much more money for it."

The next day when the king got the gold cup, he said to the rich man, "What a beautiful cup! I'll give you something for it. Please take the great orange."

小题1:What did the old man have in his garden?

A.An orange tree

B.Watermelons

C.The king

D.A gold cup小题2:What did the old man find one day?

A.He found there was a big watermelon in his gardon.

B.He found one of the oranges was as big as a watermelon.

C.He found the rich man had a gold cup.

D.He found the king liked big oranges very much..小题3:Who did the old man give the big orange to?

A.A rich man.

B.The king,

C.Himself.

D.His friend.小题4:What did a rich man think when he heard of the story?

A.He was happy for the old man.

B.He wanted to know why the king gave the old man so much money.

C.He wanted to get the orange.

D.He thought the king would give him much money if he gave the king his gold cup.小题5:Was the rich man very happy at last?

A.Yes, he was.

B.No, he wasn’t.

C.We don’t know.

D.Yes, he is.

题型:探究题

食品保鲜膜按材质分为聚乙烯(PE)、聚氯乙烯(PVC)、聚偏二氯乙烯(PVDC)等种类。PVC被广泛地用于食 品、蔬菜外包装,它对人体有潜在危害。下列有关叙述不正确的是 [ ]

A.PVC保鲜膜属于链状聚合物,在高温时易熔化,能溶于酒精

B.PVC单体可由PE的单体与氯化氢加成制得

C.鉴别PE和PVC,可把其放人试管中加热,在试管口放置一湿润的蓝色石蕊试纸,如果试纸变红,则是 PVC;不变红,则为PE

D.等质量的聚乙烯和乙烯燃烧消耗的氧气不一定相等

题型:探究题

简述政府债券的优点

题型:探究题

系统发生故障无法正常处理往来账业务应按照()原则立即报告会计和技术部门。

A.先报告、后处理

B.尽快回复运行

C.优先保障外币清算处理中心运行

D.先处理、后报告

题型:探究题

对党组织的问责方式不包括()

A.改组

B.通报

C.检查

D.批评

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