ELF Extremely Low Frequency - ορισμός. Τι είναι το ELF Extremely Low Frequency
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Τι (ποιος) είναι ELF Extremely Low Frequency - ορισμός

THE 3-30 HZ RANGE OF THE ELECTROMAGNETIC SPECTRUM
Extremely Low Frequency; Extremely Low Frequencies; Super extremely low frequency; Super Extremely Low Frequency; Below Extremely Low Frequency Band; ELF wave

Extremely low frequency         
Extremely low frequency (ELF) is the ITU designation for electromagnetic radiation (radio waves) with frequencies from 3 to 30 Hz, and corresponding wavelengths of 100,000 to 10,000 kilometers, respectively. In atmospheric science, an alternative definition is usually given, from 3 Hz to 3 kHz.
Low-frequency oscillation         
TECHNIQUE IN ELECTRONIC MUSIC
Low-frequency oscillator; Low Frequency Oscillation; Low frequency oscillator; Low Frequency Oscillator; Low frequency oscillation
Low-frequency oscillation (LFO) is an electronic frequency that is usually below 20 Hz and creates a rhythmic pulse or sweep. This is used to modulate musical equipment such as synthesizers to create audio effects such as vibrato, tremolo and phasing.
Elf (musical)         
  • 2010 Broadway cast
MUSICAL
Elf the Musical; Elf, The Musical; Elf (Broadway musical); Elf: The Musical
Elf is a musical based on the motion picture of the same name, with a score by Matthew Sklar and Chad Beguelin. The book is adapted by Bob Martin and Thomas Meehan from the 2003 film.

Βικιπαίδεια

Extremely low frequency

Extremely low frequency (ELF) is the ITU designation for electromagnetic radiation (radio waves) with frequencies from 3 to 30 Hz, and corresponding wavelengths of 100,000 to 10,000 kilometers, respectively. In atmospheric science, an alternative definition is usually given, from 3 Hz to 3 kHz. In the related magnetosphere science, the lower frequency electromagnetic oscillations (pulsations occurring below ~3 Hz) are considered to lie in the ULF range, which is thus also defined differently from the ITU radio bands.

ELF radio waves are generated by lightning and natural disturbances in Earth's magnetic field, so they are a subject of research by atmospheric scientists. Because of the difficulty of building antennas that can radiate such long waves, ELF frequencies have been used in only a very few human-made communication systems. ELF waves can penetrate seawater, which makes them useful in communication with submarines, and a few nations have built military ELF transmitters to transmit signals to their submerged submarines, consisting of huge grounded wire antennas (ground dipoles) 15–60 km (9–37 mi) long driven by transmitters producing megawatts of power. The United States, Russia, India, and China are the only countries known to have constructed these ELF communication facilities. The U.S. facilities were used between 1985 and 2004 but are now decommissioned.