The terahertz, abbreviated THz, is a unit of electromagnetic (EM) wave frequency equal to one trillion hertz (10¹² Hz). The terahertz is used as an indicator of the frequency of infrared (IR), visible, and ultraviolet (UV) radiation. An EM wave having a frequency of 1 THz has a wavelength of 0.3 millimeters (mm), or 300 micrometers (?). An EM wave of 540 THz is in the middle of the visible-light spectrum. Wireless transmissions and computer clock speeds are at frequencies far below 1 THz. The terahertz is not commonly used in computer and wireless technology, although it is possible that a microprocessor with a clock speed of 1 THz might someday be developed. At present, the terahertz is of interest primarily to physicists and astronomers. More commonly-used units of frequency are the kilohertz (kHz), equal to 1,000 Hz or 10^-9 THz, the megahertz (MHz), equal to 10⁶ Hz or 10^-6 THz, and the gigahertz (GHz), equal to 10⁹ Hz or 0.001 THz