Hertz Hertz The hertz (symbol: Hz) is the derived unit of frequency in the International System of Units (SI) and is defined as one cycle per second. It is named for Heinrich Rudolf Hertz, the first person to provide conclusive proof of the existence of electromagnetic waves. Hertz are commonly expressed in multiples: kilohertz (10 Hz, kHz), megahertz (10 Hz, MHz), gigahertz (10 Hz, GHz), terahertz (10 Hz, THz), petahertz (10 Hz, PHz), and exahertz (10 Hz, EHz). Some of the unit's most common uses are in the description of sine waves and musical tones, particularly those used in radio- and
Langmuir (unit) Langmuir (unit) The langmuir (symbol: L) is a unit of exposure (or dosage) to a surface ("e.g." of a crystal) and is used in ultra-high vacuum (UHV) surface physics to study the adsorption of gases. It is a practical unit, and is not dimensionally homogeneous, and so is only used in this one field. It is named after American physicist Irving Langmuir. The langmuir is defined by multiplying the pressure of the gas by the time of exposure. One langmuir corresponds to an exposure of 10 Torr during one second. For example, exposing a surface to a gas pressure of