题目:现代照相机、摄像机所用的光学镜头是可变焦距的.当物距改变时,可以改变镜头到“屏”的像距(即调焦)仍可获得清晰的像,如果被拍摄物体远离镜头而去,则镜头的焦距应该如何变化?同学们要想正确地解答这道题,就必须先弄懂一些有关摄影的小知识1.调焦与变焦距的区别我们知道,当物体放在凸透镜二倍焦距以外时,在底片上就能得到倒立、缩小的实像,且 Title: The optical lens used in modern cameras and camcorders is a variable focal length. When the object distance changes, the image distance from the lens to the “screen” can be changed (ie focusing) and a clear image can still be obtained if the subject is photographed. If you go away from the camera, how does the focal length of the lens change? If students want to correctly answer this question, they must first understand some little knowledge about photography. 1. The difference between focusing and zooming. We know that when the object is placed When the convex lens is outside the double focal length, an inverted and reduced real image can be obtained on the negative film, and