题干

如图,将焦距为10厘米的凸透镜置于光具座的C点处,蜡烛、光屏分置于光具座上透镜两侧,调整透镜和光屏的中心大致与烛焰的中心在____ 高度,以保证烛焰的像能成在光屏____ .将蜡烛置于A点,应在____ 间移动光屏找像(选填“CD”、“DE”或“EF”),直至光屏上的像最清晰;将蜡烛移至B点,移动光屏找像,光屏上的像将____ (选填“变大”、“不变”或“变小”).

 

上一题 下一题 0.0难度 选择题 更新时间:2015-03-23 05:26:11

答案(点此获取答案解析)

同一,中央,DE,变大

同类题5

阅读理解

    My dad was in the Air Force. When I was a kid, we moved every few years. That meant a lot of good-byes. It also meant getting used to a whole new community and a whole new school each time we moved. I can still feel what it was like to have to walk into the new school---that sinking feeling in my belly, that heaviness in my throat. It would always take time for me to learn how everything worked, what was cool and what not. It was always a struggle to find where I could fit in.

    Already shy, I didn't have much self-confidence in my friend-making abilities. I was the girl walking in the halls with her head down, panicking. When I spoke, you could hardly hear my soft voice. I was nervous and doubted myself a lot.

    It was very hard not having a history with everyone else. I was an outsider. But what I did have was soccer. Wherever I went, I knew that I could fit it with the soccer ball. The soccer team meant a familiar place and immediate friends for me. I could express myself and feel good about myself on the field. Playing hard helped to get rid of all my nervousness.

    Throughout our lives, our self-respect goes down when we feel like a failure, and it goes up when we feel successful. Doing something well, being praised, and feeling loved goes a long way. We all need to explore opportunities where we can be good at something and feel good about ourselves. Physical activity and sport participation is a terrific way to build up our sense of self-confidence and self-worth.