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
Stilb (unit) meter. The current national standard for SI in the United States discourages the use of the stilb. formula_1 formula_2 formula_3 formula_4 formula_5 Other units of luminance: Stilb (unit) The stilb (sb) is the CGS unit of luminance for objects that are not self-luminous. It is equal to one candela per square centimeter or 10 nits (candelas per square meter). The name was coined by the French physicist André Blondel around 1920. It comes from the Greek word "stilbein" meaning "to glitter". It was in common use in Europe up to World War I. In North America self-explanatory terms such as