问题 实验题

(4分)为了探究光反射时的规律,小明进行了如图所示的实验:

(1)图中的光屏是一个可折转的硬纸板,此光屏在实验中的作用是:① ________________          ; 

②用来验证                             

(2)在探究反射角与入射角的关系时,小明同学分别测出了反射角、入射角分别是400,于是他就得出了反射角等于入射角的结论。请问他这样做是否正确? ________________ ,理由是________________ 。

答案

(1)显示光路 三线共面 (2)不正确 具有偶然性,应该多测几组数据。

题目分析:(1)沿着纸板入射光线,可以能够具体显示出光路。纸板是一个平面,可以观察三线是否共面。(2)只测量一次实验数据就得出结论具有偶然性,不能有效减小误差,应该多测几组数据。

完形填空
完形填空。
     We are lucky to live in a rich country where we have many things. However, most of us usually  1  some
things.
     Electricity is one thing  2  we waste most. Lights, TVs,  3  and other things are often kept on even when
no one is using them. We should turn them off when we do not need them. It  4  less than a second to do it.
Anyhow, not wasting electricity save money, because we do not have to  5  the electricity we do not use.
     The second thing that we often waste is water. Fresh water is precious*,  6  it shouldn't be wasted. It is
only a simple matter of turning off a tap*. I am sure  7  can do this easily if he wants to. 
      8  big waste is food. My mother  9  cook so much food that much of it was thrown away. I told her we
had wasted so much  10 . She thought I was right and now cooks  11  what we can eat.
     It is not  12  to be wasteful. I find there is a simple  13  of not wasting things. That is to use only what
we  14 . Do not touch what we do not need.  15  this way we can stop being wasteful.
( )1. A. use      
( )2. A. what      
( )3. A. radios    
( )4. A. brings    
( )5. A. afford    
( )6. A. though    
( )7. A. nobody    
( )8. A. Others      
( )9. A. planned to  
( )10. A. electricity 
( )11. A. mainly   
( )12. A. right    
( )13. A. way      
( )14. A. buy      
( )15. A. On       
B. wash   
B. that   
B. apples  
B. costs   
B. save    
B. because  
B. something
B. Other   
B. used to  
B. water   
B. only   
B. fine    
B. thing   
B. need   
B. In      
C. waste    
C. whose    
C. bikes    
C. keeps    
C. pay for   
C. so       
C. everybody  
C. Another   
C. was able to
C. food     
C. mostly   
C. bad     
C. plan       
C. bring    
C. For     
D. forget       
D. who          
D. doors        
D. takes        
D. care for     
D. but          
D. nothing      
D. The other    
D. was afraid to
D. money        
D. specially    
D. necessary    
D. project                        
D. get          
D. At           
填空题