题干

实验小组的同学用如图所示的装置来探究“近视眼的缺陷”.他们用蜡烛代表眼睛观察的物体,用凸透镜代表眼球的晶状体,用光屏代表视网膜.为判断近视眼不戴眼镜时物体成的像在视网膜前还是视网膜后,小明提出如下实验方案:先不给凸透镜戴眼镜,让烛焰在光屏上成像,然后给凸透镜戴上眼镜,移动光屏,再次让烛焰在光屏上成像,比较两次像距的大小.实验时,要注意调节烛焰、凸透镜、光屏的高度,使它们的中心大致在____,这样做的目的是____.下表是小明通过实验测得的数据:

实验序号

物距u/cm

不戴眼镜的像距

v1/cm

戴眼镜的像距v2/cm

像的性质

1

45.0

12.5

13.8

倒立缩小

2

40.0

13.5

14.2

倒立缩小

3

30.0

15.0

16.0

倒立缩小

4

15.0

30.0

35.6

倒立放大

小组同学通过分析认为,第____次数据是无效的,原因是____.分析表格中的数据,我们发现,v1____(>/=/<)v2,所以近视眼镜的作用是使像____(远离/靠近)晶状体.那么近视眼不戴眼镜时,物体通过晶状体所成的像落在视网膜的____(前/后)方.

小华进一步思考后提出另一实验方案:

先给凸透镜戴上眼镜,让烛焰在光屏上成像,然后取下眼镜,再让烛焰在光屏上成像,比较两次像距的大小.

你认为小华的实验方案____(可行/不可行).

上一题 下一题 0.0难度 选择题 更新时间:2019-05-24 08:02:32

答案(点此获取答案解析)

凸透镜的主光轴上,烛焰的像成在光屏的中央,4,眼睛不可能成倒立放大的实像,<,远离,前,可行

同类题3

    In the most southern part of our planet, there's a place that's covered with snow and ice all year round. But it has the clearest and cleanest air. Amazingly, in this place, the sun sometimes hangs even in the midnight sky. This place is Antarctica (南极洲): the coldest, windiest and harshest (恶劣的) place on the Earth.
    As the world's least-known place, Antarctica is of great interest to scientists around the world. In 1983, China joined the Antarctic Treaty (《南极条约》). The treaty made Antarctica a peaceful place for member countries to do scientific research. During 30 years, China has sent many scientists to Antarctica. They mostly look at the resources under the icy land and do research about climate change and marine (海洋的) biology.
    Antarctica is a place with fantastic views. However, life there is very hard. Food is one of the biggest problems. Frozen (速冻) food which can be heated easily is people's daily food. Fresh vegetables are hard to grow in the cold weather. Therefore, scientists often eat dried or canned vegetables.
    Sleep is also troublesome. In Antarctica, summer lasts from November to March. During this period, Antarctica points to the sun and receives sunlight 24 hours a day. In order to get some sleep, scientists cover the windows with black plastic cloth to create “night”.
Working in Antarctica is dangerous, especially when meeting gale-force (七级以上的) winds. Sometimes the wind is even stronger than a typhoon. It can easily blow people away. So there are ropes that connect buildings of some research stations. People can hold these ropes to keep their balance in forceful winds.
    What's more, communicating with others is difficult. Without cables and Internet in some research stations, two-way radios are the only tools to communicate. If people want to say hello to friends and relatives, they can use satellite phones.
    Although it is challenging to work in Antarctica, scientists' passion to learn about this mysterious land will never end. It is hopeful that one day they will step every corner of this icy land.