教学中常用的幻灯机,其镜头相当于______透镜,它所成的像是倒立的、放大的______像.
幻灯机是利用凸透镜成倒立、放大的实像工作的.
故答案为:凸;实.
Find out the mistakes and correct them. 找出错误并改正。
( ) 1. I have to put on my boots on a rain day.
A B C
( ) 2. Li Ming is writing an letter in the corner.
( ) 3. The peas are in the stove.
( ) 4. I'm a 12 year old boy.
( ) 5. Danny, you should sing soft.
试计算1.3:2.6:7.4(沥青:石英粉:石英砂)耐酸沥青砂浆每立方米各种材料的净用量(已知:沥青的密度为1.1g/cm3,石英粉和石英砂的密度均为2.7g/cm3)。