2-1 Brief introduction to electromagnetic wave
Do you know what electromagnetic wave is? In fact, electromagnetic wave exists everywhere in our surrounding environment, such as electric fan, microwave oven, drier and other household appliances. But what is it on earth? Let me tell all of you!

Electromagnetic wave is a kind of energy which cannot be seen and touched, with the exception of visible light. It is produced by the interaction between electric field and magnetic field and transmitted in the space in the form of wave.