Hertz The dimension of the unit hertz is 1/time (1/T). Expressed in base SI units it is 1/second (1/s). In English, "hertz" is also used as the plural form. As an SI unit, Hz can be prefixed; commonly used multiples are kHz (kilohertz, 10 Hz), MHz (megahertz, 10 Hz), GHz (gigahertz, 10 Hz) and THz (terahertz, 10 Hz). One hertz simply means "one cycle per second" (typically that which is being counted is a complete cycle); 100 Hz means "one hundred cycles per second", and so on. The unit may be applied to any periodic event—for example, a clock might be
Collision frequency Collision frequency Collision frequency is defined in chemical kinetics and collision theory, in the background of "theoretical kinetics". If a system contains "n" type-a molecules per unit volume and "n" type-b molecules in that same unit volume, then the number of a-b collisions per unit time in that volume will be proportional to the product "nn". or, in terms of molar volumes ("[x]=n /N" where N is the Avogadro constant) By kinetic theory it can be shown that: where The collision frequency ("Z") is usually expressed in units of "moles of collisions" per unit time per unit volume: or equivalently: