由于工作的关系,常会收到一些读者关于中学物理教科书的来信.其中有的来信质疑高中物理教材选修3-4中一幅关于平面电磁波的传播图(图1),认为图中的电场分量与磁场分量同相位的画法是不对的,它们之间应该存在π/2的相位差.当然,绝大部分教师都知道这幅图是正确的,但谈起这个问题时,也感叹的确不易向学生讲明白.在人教论坛或其他BBS上,更是常见学生对于这个问题的疑惑.因此,还是非常有必要针对这个问题做进一步 Due to the work relationship, we often receive some readers’ letters about the physics textbooks of secondary schools, some of whom have questioned the propagation of plane electromagnetic waves (Figure 1) in the High School Physics Electives (3-4) Of course, most teachers know that this picture is correct, but when it comes to this question, they also lament that it is really not easy to point out Students make it clear that in the forum to teach people or other BBS is more common students doubts about this issue.Therefore, it is still very necessary to address this issue