Hertz radians per second. Thus a disc rotating at 60 revolutions per minute (rpm) is said to be rotating at either 2 rad/s "or" 1 Hz, where the former measures the angular velocity and the latter reflects the number of "complete" revolutions per second. The conversion between a frequency "f" measured in hertz and an angular velocity "ω" measured in radians per second is The hertz is named after the German physicist Heinrich Hertz (1857–1894), who made important scientific contributions to the study of electromagnetism. The name was established by the International Electrotechnical Commission (IEC) in 1930. It was adopted by
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