问题 问答题

如图,两条反射光线,是点光源S发出的光经过平面镜反射后的两条光线,试确定点光源s位置.

答案

第一种作法:先将两条反射光线反向延长交于一点S′,在通过平面镜作出S′的对称点S,即为发光点的位置,并联接S与两个反射点画出入射光线,如图所示:

第二种作法:分别过反射点垂直镜面作出法线,画出两条入射光线,两条入射光线的交点S即为发光点的位置,如图所示:

阅读理解

One day Mrs. Wilson went shopping with Tracy and Ben. They went to the supermarket in the new shopping center.

“Why do you buy things here?” Tracy wanted to know. “Because they are cheaper here than at the corner store near our home,” Mrs. Wilson said。” Help me check the prices, please.”

The Wilsons were not rich and Mrs. Wilson was always careful with her money. She looked carefully after the prices of things. She bought lots of things in the supermarket. When they got home, the children said,“ We don’t think you saved money by going to the supermarket.”

“Of course I did,” Mrs. Wilson said。. “Everything was cheaper there.” “We know,” the children said,“but we came home by taxi because we had too much to carry. The taxi fare was more than the money that you save! ”

Mrs. Wilson added everything up. Her children were right.

小题1:The things at the corner store were ______than those in the supermarket.

A.cheaper

B.nicer

C.more expensive

D.saved a little money小题2:Mrs. Wilson ______ in the end.

A.spent more money

B.paid less money

C.lost some money

D.saved a little money小题3:From the passage we know the children were _________.

A.happy

B.clever

C.tired

D.lazy小题4:Mrs. Wilson will _____________.

A.never call a taxi

B.go on buying things in the supermarket

C.buy things near her home

D.not go shopping with her children小题5:The best title for the passage is ____________.

A.Cutting Price

B.Corner Store

C.Supermarket

D.Shopping

判断题