She went to the supermarket and ______ what she needed, she left for the train station, light-hearted. A. bought B. buying C. having bought D. to have bought 答案:C12.用光子能量为2.5eV的一束光照射某光电管的阴,能够发生光电效应,这时给光电管加上反向当所加反向电压大于或等于0.60V时,光电子不能到达阳极,根据以上信息,可求出该光电管阴极材料的逸出功为1.9eV;光电子的最大初动能等于0.6eV.