题干

如图为中学实验室中常用的显微镜,请回答:

(1)使用显微镜对光的正确程序是:____ .

①选遮光器上适宜的光圈对准通光孔 ②转动转换器,使物镜对准通光孔 ③左眼注视目镜(右眼睁开),转动反光镜调节出一个白亮的视野.

(2)观察时应先选用____ 物镜.(填“高倍”或“低倍”)

(3)显微镜下视野较暗,这时应转动________ 调节视野的亮度,如果物象不够清晰,调节____ 使物象更清晰.

(4)现有一台显微镜,它有两个目镜(放大倍数分别是5×和15×),两个物镜(放大倍数分别是10×和40×),那么这台显微镜的最大放大倍数是____ 倍.如果物像在视野的左下方,要使物像向视野中心移动,应将载玻片向____ 移动.

(5)视野中若有一个污点,擦拭目镜和移动装片时都不能移动,说明污点很可能在____上.

(6)在光线较暗时,应选用____ 面镜对着光源.

(7)将写有字母“P”的载玻片放在显微镜下观察,在视野中看到的图象是____ .

上一题 下一题 0.0难度 选择题 更新时间:2019-03-08 12:10:35

答案(点此获取答案解析)

③①③,低倍,遮光器,反光镜,细准焦螺旋,600,左下方,物镜,凹面镜,d

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完形填空

     When people think of tigers, they think: strong and dangerous. But now, the big animal is calling for our help.

     There were once eight kinds of   1   in the world, but three died out during the 20th century. In the last 70 years, the   2   of Siberian tigers (东北虎) has gone from as many as 300 to   3   22 somewhere. The Siberian tiger has been   4   dying out completely. If the government doesn't make any efforts, it's quite   5   that there will be no more Siberian tigers in China in ten to twenty years.

     In order to double the number of wild tigers in the   6   ten years, the World Wildlife Fund for Nature has started a program recently. It   7   save wild tigers and put an end to tiger hunting and killing. China, together with twelve other   8  , has joined in.

     Wild animals, such as red deer and wild pigs, are the main   9   of the tigers. The hunting of these animals is the greatest threat(威胁) to tigers. So the most important thing is   10   the animals that tigers eat. To protect the wild tigers, we need to call on more people to stop eating and hunting wild animals.

 1 A. pigs        B. tigers             C. deer              D. lions

 2 A. name       B. kind              C. number           D. type

 3 A. less than    B. more than        C. bigger than       D. larger than

 4A. in need of   B. in danger of      C. in front of  D. in spite of

 5 A. possible     B. impossible   C. necessary         D. unnecessary

 6 A. last        B. next             C. past             D. first

 7 A. aims to     B. used to           C. refuses to         D. aimed to

 8 A. cities        B. provinces          C. countries          D. places

 9 A. friends      B. food               C. members          D. relatives

 10 A. to sell     B. to kill           C. to save           D. to buy