Becquerel Becquerel The becquerel (; symbol: Bq) is the SI derived unit of radioactivity. One becquerel is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The becquerel is therefore equivalent to an inverse second, s. The becquerel is named after Henri Becquerel, who shared a Nobel Prize in Physics with Pierre and Marie Curie in 1903 for their work in discovering radioactivity. As with every International System of Units (SI) unit named for a person, the first letter of its symbol is uppercase (Bq). However, when an SI unit is spelled out
Bar (unit) (symbol: cbar), and millibar (symbol: mbar or mb). The notation bar(g), though deprecated by various bodies, represents gauge pressure, i.e., pressure in bars above ambient or atmospheric pressure. The bar is defined using the SI derived unit, pascal: ≡ 100,000 Pa ≡ 100,000 N/m. Thus, is equal to: and 1 bar is approximately equal to: Notes: The word "bar" has its origin in the Greek word (), meaning weight. The unit's official symbol is bar; the earlier symbol b is now deprecated and conflicts with the use of b denoting the unit barn, but it is still encountered, especially as