无线电波是频率较低的电磁波。无线电波按波长的不同划分为超长波、长波、中波、短波、超短波和微波;按频率的不同,可划分为甚低频、低频、中频、高频、甚高频、特高频、超高频和极高频。超长波(VLF甚低频):频率范围在3～20kHz之间。主要用长波(LF低频):频率范围在30～300kHz主要用于地下岩 Radio waves are less frequent electromagnetic waves. Radio waves are divided into ultra-longwave, longwave, mediumwave, shortwave, ultrashortwave and microwave according to the wavelength. According to the frequency, they can be divided into very low frequency, low frequency, medium frequency, high frequency, very high frequency, very high frequency, Frequency and very high frequency. Long wave (VLF very low frequency): The frequency range between 3 ~ 20kHz. The main use of long-wave (LF low frequency): the frequency range of 30 ~ 300kHz mainly used for underground rock