题目

照相机的镜头相当于一个凸透镜,在使用照相机拍照时,景物距镜头的距离要________(填“大于”“等于”或“小于”)镜头的二倍焦距；物体在底片上所成像的大小________(填“大于”“等于”或“小于”)实际物体的大小. 答案：【答案】大于 小于 【解析】凸透镜成像时，物距u＞2f，成倒立缩小的实像，应用是照相机。使用照相机时，物距大于二倍焦距，即景物和镜头的距离要大于镜头的二倍焦距；照相机底片上成倒立缩小的实像。根据对话内容，在空白处填写适当的话语（话语可能是一个句子，也可能是一个短语或一个词），使对话完整。A: Ann's birthday is coming.  I need to-get some money to buy her a present. __1__?B: If l were you,  1 would ask my parents for some money.A: No, __2__.  I don't want to make them unhappy because they don't want me to make friends at school.B: __3__ borrowing some from your friends?A: No. They don't have any money, either.B: Go to your uncle and help him sell clothes.  Maybe he would like to give you somc.A: __4__ I'll try that.B: What would you like to buy?A: Maybe a scarf and some flowers.B: Now flowers are very expensive, you know.A: But she __5__ flowers, especially roses. I'll  have to buy her some roses.  I must go now.  I have to     go to see my uncle. B: See you.