上教版高中一年级物理第七章第六节“振动”中安排了一个描绘振动图像的实验：把钢锯条的一端固定在铁架台上，另一端缚一支蘸有墨水的毛笔，拨动锯条时，毛笔的振动可看成简谐振动，调节毛笔的位置使笔尖刚能接触到放在它下面的一张纸片。如果在毛笔振动的同时，沿着垂直于笔 In the sixth edition of the first edition of the physics of the senior high school education, “Vibration” in the seventh chapter was arranged an experiment depicting a vibration image: one end of a hacksaw blade was fixed on a metal stand, and the other end was tied with a brush with ink and plucked. When the saw blade is in use, the vibration of the brush can be considered as a simple harmonic vibration. The position of the brush is adjusted so that the pen point can just touch a piece of paper placed under it. If the brush vibrates, it is perpendicular to the pen