Radio atmospheric km. For ELF waves (< 3 kHz), ray theory becomes invalid, and only mode theory is appropriate. Here, the zeroth mode begins to dominate and is responsible for the second window at greater distances. Resonant waves of this zeroth mode can be excited in the Earth–ionosphere waveguide cavity, mainly by the continuing current components of lightning flowing between two return strokes. Their wavelengths are integral fractions of the Earth's circumference, and their resonance frequencies can thus be approximately determined by "f" ≃ "mc"/(2π"a") ≃ 7.5 "m" Hz (with "m" = 1, 2, ...; "a" the Earth's radius and "c" the
Radio Waves (song) Radio Waves (song) "Radio Waves" is the opening track from Roger Waters' second solo studio album, "Radio K.A.O.S." It was chosen as the lead single for the album, released worldwide in May 1987. "Radio Waves" introduces the main character, Billy, a disabled man who finds a way to talk and become friends with a radio DJ. Billy is gifted and has the miracle of hearing and interpreting radio waves in his head. He explores a cordless phone which was hidden in his wheelchair by his brother Benny, after destroying and robbing a store. Recognising its similarity to a radio, he