问题 选择题

如图,一束光线由空气射向水面,那么这束光线的反射角和折射角可能为:

[ ]

A、50°,60°

B、50°,30° 

C、40°,60°

D、40°,30°

答案

答案:B

题目分析:法线过入射点与镜面垂直,入射光线与镜面之间的夹角为40°,则入射角为50°,根据反射角等于入射角,所以反射角也为50°.
而光从空气中斜射入水中时,折射角小于入射角,所以那么这束光线的反射角和折射角可能为50°,30°.
故选:B.
阅读理解

阅读理解

       John likes chocolates very much, but his mother doesn't give him. They are bad for his teeth, she

thinks. But John has a very nice grandfather. The old man loves his grandson very much. And sometimes

he buys John some chocolates. Then his mother lets him eat them, because she wants to make the old

man happy.

       On Sunday evening, it is John's seventh birthday. He says, "Please, God(上帝), make them give me

a big box of chocolates for my birthday,"His mother says, " God can't hear you. Don't shout(喊)."                " I know, "says the clever boy with a smile(微笑). " But my grandfather is in the next room, and he

can!"

1. John's mother thinks________.      

A. John's teeth are bad          

B. chocolates are good for her teeth

C. chocolates are bad for John's teeth  

D. John likes cakes

2. Why does John's mother let him eat chocolates sometimes?

A. Because John wants to eat them.  

B. Because John's father buys some chocolates for him.

C. Because she is happy.    

D. Because she wants to make John's grandpa happy.

3. Why does John shout? Because he wants to make _________hear him. 

A. his grandpa        

B. his grandma      

C. his mother      

D. his father

 4. Which one is right?   

A. The grandfather is bad.      

B. John studies hard in his school.

C. John is clever.            

D. John's mother doesn't love him.

5. What day is John's seventh birthday?       

A. Saturday      

B. Friday    

C. Tuesday          

D. Sunday

单项选择题