First of all, the import part
First of all, through an interesting advertisement, arouse students' curiosity and stimulate their interest in learning. Then, review what you have learned in the last two sections. Finally, the new course "How does light spread" is introduced, and how does light spread is put forward by asking questions.
Second, extract life experience for preliminary verification.
The students conjectured that light travels in a straight line. I'm asking, then why are you all so sure? What phenomena have you observed in your life that make you think so? Students recall the straight light they saw in their lives.
Third, it is verified again through experiments.
Next, two experiments were arranged for the students, from shallow to deep, and promoted layer by layer. Let the students finish the first experiment first, and use the hollow plastic pipe and flashlight to design the experiment, which proves that light travels along a straight line. Students found through experiments that when the pipe is straight, you can get a light spot on the table or other places with a flashlight, but after the pipe is bent, you can't see the light spot.
Fourthly, the explanation of shadow formation.
In fact, the shadow is formed because light travels in a straight line. Students can only understand that the propagation of light was blocked in the past, so there was no spot, only shadow, and they can't think that it should be explained by the linear propagation of light. So we can only guide them to imagine that if light energy bypasses an object by turning, that is, when light does not necessarily travel in a straight line, it can also bypass the object and a light spot appears on the opposite side of the object. We only see shadows, because light travels in a straight line and does not turn.