“Frequency” describes the number of times per second that an electrical incident takes place, and is expressed in Hertz (abbreviated Hz). 10 Hz means that a signal changes polarity or pulses 10 times per second. Kilo (abbreviated K) means 1,000 (thousand), Mega (abbreviated M) means 1,000,000 (million), and Giga (abreviated G) means 1,000,000,000 (billion). 10 KHz is the same as 10,000 Hz. 10 MHz is the same as 10,000,000 Hz.
Frequencies that can be heard are called Audio frequencies (abbreviated AF), and the rest of the frequencies (which are easily transmitted through the air) are commonly called Radio frequencies (abbreviated RF). (Although Audio frequencies are technically Radio frequencies as well) The dividing line between Audio and Radio frequencies is not consistant, varying with different people and industries. Frequencies below 100,000 Hz are audible to some animals and will not produce significant side effect frequencies that can be easily transmitted through the air. 100,000 Hz. is one appropriate dividing line between Audio and Radio frequencies.
Electrical signals act differently at different frequencies. A characteristic called “skin effect” (which is not confined to skin) causes a conductor to resist the flow of electricity as a function of frequency- the higher the frequency, the greater the resistance to the flow of electricity. At low frequencies, say 60 Hz (household electricity), a sufficiently high voltage has the ability to penetrate through the body and create cardiac arrest. At high frequencies, say 1 GHz (low frequency radar), the same amplitude voltage can only penetrate a fraction of an inch into a body, and will only create a surface skin burn called a RF burn.