Extremely low frequency (ELF) is the designation given by the International Telecommunication Union (ITU) for radio waves or electromagnetic radiation with frequencies that range from just 3 Hz to 30 Hz and with corresponding wavelengths .
Extremely low frequency (ELF) is the designation given by the International Telecommunication Union (ITU) for radio waves or electromagnetic radiation with frequencies that range from just 3 Hz to 30 Hz and with corresponding wavelengths .