问题 选择题

用如图所示的实验装置观察光的薄膜干涉现象。图中左侧是洒有食盐的酒精灯火焰,右侧是竖立的附着一层肥皂薄膜的金属丝圈,关于该实验,下列说法正确的是

A.观察时应当在火焰的同侧面向薄膜观察火焰的象

B.观察时应当在火焰的异侧透过薄膜观察火焰的象

C.将金属丝圈在其所在的竖直平面内缓慢旋转90°,干涉条纹保持原形状不变

D.将金属丝圈在其所在的竖直平面内缓慢旋转90°,干涉条纹也将同方向旋转90°

答案

AC

本题考查薄膜干涉实验现象

当光源发出的光照射到肥皂膜上时,从膜的前后两面分别反射两列光为相干光,当当光程差为波长的整数倍时呈现亮条纹,当光程差为半个波长的奇数倍时呈现暗条纹.相同的高度肥皂膜的厚度相同,故出现水平的明暗相间的干涉条纹.

在转动金属丝圈的过程中,由于两层薄膜的厚度不变,故反射光形成的光程差也不会发生变化,故产生的干涉条纹仍保持原来的状态不变;

有掌握了各种物理现象的产生机理才能正确解答相关题目,故在日常学习中不但要知其然,更要知其所以然.

阅读理解

根据短文内容在下面的每个句子的空格中填上一个词,使其意思与原文相符。

       Mr and Mrs Black live in London. Mr. Black drives a car in a factory and Mrs. Black teaches in a school.

They have a daughter and two sons. The daughter is five and the sons are only one year old. They were born

on the same day and they look the same. Mrs. Black always dress them in the same shirts and trousers, so it's

hard to tell who they are. Mr. Black can hardly differentiate (区分) them. Mr. and Mrs. Black have no time to

look after their children. They have to hire a servant (雇佣一个佣人), Alice. The girl is kind and they all like

her.   

       Today Mrs. Black has to go to the hospital. She says to Alice,"Bath Tom and Tim and dress them the clean

clothes."

       "OK, Mrs. King," says Alice."But I can't differentiate them."

       "Don't worry," says Mrs. Black."Ann can tell you about it."

       Soon Alice finishes bathing the two children. She puts them on the bed and wants to dress them. She asks,

"Which is Tom, Ann?

       "I'm sorry," answers Ann."I can't differentiate them. I only know Mummy always puts Tom on the left and

Tim on the right."      

1. Mr Black is a __________ and his wife is a __________.

2. There are _________ people in Mr. Black's family.

3. Mr. Black's two sons are ________ and Mrs. Black always dresses them the same ________.

4. The Blacks are _______ busy _______ they can't look _______ their children. So the hire Alice.

5. From the story we know that only _______ ________ can differentiate the two babies.      

单项选择题