图1所示的光路图、描述的是一种极常见的折射现象,中学物理课本从初中到高中,包括不同的版本,都选用了,真可谓典型.从初中到高中,学生理当学好,然而,通过高三学生的提问,对高三学生的测试,发现学生仍是糊涂的:测试时,大量学生答M′在M的正上方,且有少数学生答 M′在M的左上方;好学生还在问:”为什么M′在M的右上方?”由此可见,学生并未学好. The optical path diagram shown in Fig. 1 describes a very common refraction phenomenon. The middle school physics textbooks have been selected from junior high school to high school, including different versions. This is really typical. From junior high school to high school, students should learn well, however, Through high school students’ questions and testing of high school students, they found that the students were still confused: When testing, a large number of students answered M’ directly above M, and a small number of students answered M’ at the top left of M; Asked: “Why M’ is on the upper right of M?” Thus, the student did not learn well.