2-2 Knowledge of electromagnetic wave
Electromagnetic wave is also known as “electromagnetic radiation”. The planet is a large electromagnetic field in itself and electromagnetic wave will display different appearances depending on the environment and variety. According to the effect of radiation on organisms, the common electromagnetic wave can be classified into “ionizing radiation” and “non-ionizing radiation”.
“Ionizing radiation” is very dangerous. It can damage biological cell elements and has the accumulative effect just like X-ray, gamma-ray, cosmic rays, etc.

“Non-ionizing radiation” will not damage biological cell elements and have no accumulative effect. The electromagnetic wave emitted by our favorite mobile phones and base station and sunlight in daily life belong to “non-ionizing radiation”.