题目

My English teacher gave us a horrible job today．She told us what we would have to prepare a ten-minute speech for Tuesday．I can’t stand speaking in front ofthe class．Anyway, I asked my teacher if I could do something different—like a writing report．I told her how nervously I would get when speak before the class．My teacher explained me that she couldn't change that．While she did have some advices．She encouraged me to get to work right away．She said if I practice my speech ahead of time，I would feel the more comfortable．As a result of his warm words，I decided t19．沈细致同学做“探究凸透镜成像规律”的实验．请你帮助他完成下列内容：（1）他先将一块凸透镜放在光具座上，当烛焰、透镜及光屏的位置如图1所示时，恰能在光屏上得到一个清晰、等大烛焰的像，则该凸透镜的焦距为10cm；（2）当蜡烛、透镜、光屏的位置如图2所示时，此时恰能在光屏上出现一个清晰烛焰的像，这个像是倒立（选填“倒立”或“正立”）、放大（选填“放大”、“等大”或“缩小”）的实像；将蜡烛向靠近凸透镜的方向移动2cm，光屏上再次成的清晰的像将变大（选填“变大”、“变小”或“不变”）．保持透镜位置不变，将蜡烛、光屏的位置互换，能（选填“能”或“不能”）在光屏上成一清晰像．（3）实验中，光屏上已呈现蜡烛清晰、完整的像，但他不小心用手指指尖触摸到了凸透镜，这时光屏上会出现烛焰完整的像．（选填“指尖的像”、“指尖的影子”、“烛焰完整的像”或“烛焰部分的像”）