题目

The World Wide Web is so common and popular that not a day goes by when we don’t use the World Wide Web. Today it has become almost as important to every family as food and water! This year, the World Wide Web has turned 25 years old. What many people don’t know is that the web was at first created to improve communication between thousands of scientists in Switzerland. In 1989, Tim Berners-Lee was a 34-year-old British physicist working as a software engineer at CERN, the European Organization for Nuclear Research in Switzerland. Since CERN was a huge organization with thousands of完成凸透镜的光路图___． 【解析】图是凸透镜：入射光线与主光轴平行，则折射光线过焦点；过光心的光线经凸透镜折射后传播方向不改变．如下图所示