实验目的：
研究光控原理。
实验器材：
无弦琴。
实验过程：
1、将电源插头插入插座，打开电源开关。
2、手指并拢，挡住键盘上的小孔，注意听。
3、实验完毕，断开220V电源开关并小心取下电源插头。
探究问题：
1、手挡住了光线，为什么会听到琴声？
2、同样做挡光的动作，为什么听到的音调不同？
3、手挡光的位置不同，对实验有怎样的影响？
4、手挡光的时间长短不同，对实验有怎样的影响？
实验结论与体会：
（以下由学生总结并交流，也可由教师引导得出。）
注意事项：
演奏简单乐曲时，手在换位时应快速向后拉，手应距孔近些。
Musical instrument without the strings
Experimental purpose:
Researching the light controlling principle
Experimental equipment:
Musical instrument without the strings
Experimental process:
1.Connect the power supply, and turn on the switch.
2.Close the fingers to cover the eyelet in the fingerboard, and listen carefully.
3.Cut off the power supply and pull out the switch carefully.
Researching issues:
1.Why can we hear the sound with the hand shielding the light?
2.Why the sound is different again stopping the light?
3.What is the influence on the experiment at the different site of the hand stopping the light?
4.What is the influence on the experiment with the different time of stopping the light?
Experimental conclusions and the experience:
The followings can be concluded and discussed by the students, or guided to get by the teachers
Caution:
When play the simple music, the hand should quickly pull backward when changing the place, and the hand should be near the eyelet.
