题目

Odiand remembers like it was yesterday working in an expensive French restaurant in Denver．The ice cream he was serving fell onto the white dress of a rich and important woman． ．Thirty years have passed, but Odiand can' t get the memory out of his mind, nor the woman' s kind reaction．She was shocked, regained calmness and, in a kind voice, told the young Odiand,  “It' s OK．It wasn' t your fault． When she left the restaurant, she also left the future Fortune 500 CEO with a life lesson: You can tell a lot about a person by the way he or she treats the waiter． Watch out for anyon小明用凸透镜、蜡烛、光屏和刻度尺等器材，探究凸透镜成像的规律。（9分）（1）如图所示，将凸透镜正对着太阳光，把光屏置于另一侧，改变光屏与凸透镜间的距离，直到光屏上出现一个        的光斑，测得凸透镜的焦距是       cm。（2）小明将烛焰、凸透镜和光屏的中心调到同一高度，无论怎样移动光屏，都不能得到清晰的像原因可能是                。实验一段时间蜡烛变短，要使烛焰像仍然成在光屏的中心，应将凸透镜向       移动。（3）小明现把蜡烛放在距凸透镜40 cm处，在凸透镜另一侧前后移动光屏，在光屏上可以得到一个      （填“放大”、“缩小”或“等大”）的    （填“实”或“虚”）像。若小明在凸透镜前放置一个凹透镜，要想在光屏上接收到清晰的像，应该将光屏向    （选填“靠近”或“远离”）凸透镜的方向移动。（4）小明用三个焦距不同的凸透镜进行实验，数据记录如上表。分析表中数据可知，在物距一定时，凸透镜的焦距越大，所成实像的像距      ；根据你所学凸透镜成像规律分析，此时所成像的大小      。（均选填“越大”、“越小”或“不变”）。