题目

If you've not heard that the decade-old princess-culture is causing problems—especially if you're a parent—you must be actively working to avoid it. The latest study adding fuel to the fire comes out of Brigham Young University and finds that the Disney princess obsession can be harmful to girls. “I think parents think that the Disney princess culture is safe. That’s the word I hear time and time again—it’s safe.” Lead study author Sarah M. Coyne of the Mormon institution in Utah noted in a press release. “But if we’re fully jumping in here and really embracing (accept某次实验时,蜡烛的烛焰、凸透镜的光心及光屏的中心位于同一直线上,当烛焰与凸透镜的光心相距30 cm时,可在光屏上成缩小、倒立的实像,现将蜡烛靠近凸透镜移动5 cm,下列说法正确的是 ( )A. 一定成倒立、放大的实像B. 一定成倒立、缩小的实像C. 可能成倒立、等大的实像D. 无法判断 C 【解析】把蜡烛放在凸透镜30cm处，光屏上可接收到缩小、倒立的实像，所以蜡烛在u＞2f,及30cm＞2f,∴f15cm如果蜡烛在远离凸透镜5cm,物距是25cm, f25cm所以光屏上可以是倒立放大的实像。