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机械波图象是教学的难点,此难点主要表现在两个方面,即依据某时刻的波形图画下一时刻的波形图;依据两个时刻的波形图求波速。笔者认为,难点的成因在于波是周期性振动在介质里的传播,振动的周期性导致了不同时刻的波形图可能具有外观上的一致性.也即波的周期性。因此,波形图的周期性,是教学难点的突破口。
The mechanical wave image is a difficult point in teaching. This difficulty is mainly manifested in two aspects, that is, according to the waveform chart of the next moment of the waveform picture at a certain moment; the wave speed is obtained according to the waveform diagrams of the two moments. The author believes that the difficulty lies in the fact that waves are the propagation of periodic vibrations in the medium. The periodicity of the vibrations causes the waveforms at different times to have the appearance consistency, that is, the periodicity of waves. Therefore, the periodicity of waveforms is a breakthrough point for teaching difficulties.