What do the Curie couple, Henrie Becquerel, Louis Harold Gray, and Ralf Sievert have in common?
These radiation pioneers defined the way we measure ionizing radiation.
Pierre and Marie Curie created curie (Ci), the first non-SI unit for measuring radioactivity. A Ci meant "the quantity or mass of radium emanation in equilibrium with one gram of radium". But later, as the understanding behind radiation advanced, it was re-defined as 3.7×10^10 decays per second of the isotope Radium 226.
Henri Becquerel, who shared a 1903 Physics Nobel with the Curies, has a different unit of radiation named after him. The becquerel (Bq) is the SI unit of radioactivity. A Bq is equal to the amount of radiation released by the per-second disintegration of one radioactive nucleus.
Either Ci or Bq tells us about the damage to biological tissues upon exposure to radiation. British physicist Louis Harold Gray came up with gray (Gy), a unit he used in the measurement of X-ray and radium radiation and their effects on living tissue. It is defined as "the absorption of one joule of radiation energy per kilogram of matter".
Just like Gray, Rolf Maximilian Sievert, a Swedish medical physicist, was also interested in the impact of radiation to the human body. He developed another unit, Sievert (Sv), to measure the health effect of low levels of ionizing radiation on the human body. It is now a critical measurement in the fields of biodosimetry and radiation protection.
Source: IAEA via Youtube