到19世纪中叶的时候，科学家对被称为电磁力这一现象中三个组成部分(指电、磁和光，译者注)已经有了相当的了解。
By the mid-19th century scientists had a fair understanding of each of the three components of electromagnetism, as the phenomenon has come to be called.
利用电子元器件设计电路 ，制作了基本控制演示仪 ，演示了最基本的温、磁、光、声控制现象 。
Using electronic components to design circuit, the basic control demonstration instrument is made, and the control phenomena of temperature, magnetism, light and voice are demonstrated.
利用旋光现象和偏振光学特性设计了一种磁光开关；
A magneto-optic switch is presented by using Faraday magneto-optic effect and the properties of optic polarization.
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