Physics · nuclei · NEET
Yes. The becquerel (Bq) is the SI unit of activity. 1 Bq = 1 disintegration (decay) per second. So if a sample has an activity of 500 Bq, exactly 500 of its nuclei break down every second. Because one decay per second is very small, real sources are often thousands or millions of Bq.
1 Ci = 3.7 x 10^10 Bq. This number came from the measured activity of 1 gram of radium-226. So 1 curie is 37 billion decays per second. To go from Ci to Bq, multiply by 3.7 x 10^10; to go from Bq to Ci, divide by 3.7 x 10^10.
The curie is far bigger. 1 Ci = 3.7 x 10^10 Bq, so one curie equals 37 billion becquerel. That is why lab and medical sources are usually written in millicurie (mCi) or microcurie (uCi), while background counts are written in Bq or kBq.
1 mCi = 10^-3 Ci = 3.7 x 10^7 Bq. 1 uCi = 10^-6 Ci = 3.7 x 10^4 Bq = 37000 Bq. Just take the curie value and multiply by 3.7 x 10^10 after converting the prefix to a plain number.
Yes, a smaller practical unit called the rutherford (Rd) is sometimes mentioned: 1 Rd = 10^6 decays per second = 10^6 Bq. It is rare in NEET, but you may see it. For NEET, focus on Bq and Ci and the conversion 1 Ci = 3.7 x 10^10 Bq.
Both. Activity R = lambda x N, where lambda is the decay constant and N is the number of undecayed nuclei. Since lambda = 0.693 / half-life, a shorter half-life gives a larger lambda and thus a larger activity for the same N. So two samples with the same number of atoms can have very different Bq values.
1 becquerel (Bq) = 1 radioactive decay (disintegration) per second. It is the SI unit of activity and is named after Henri Becquerel, who discovered radioactivity in 1896.
1 curie (Ci) = 3.7 x 10^10 Bq = 3.7 x 10^10 decays per second. It was originally the activity of 1 gram of radium-226.
Because it was defined from a physical sample, not a round number. Scientists measured that 1 gram of radium gives about 3.7 x 10^10 decays per second, and fixed the curie at that value.
2 mCi = 2 x 10^-3 Ci. Multiply by 3.7 x 10^10 Bq/Ci: 2 x 10^-3 x 3.7 x 10^10 = 7.4 x 10^7 Bq.
No. Activity is the number of atoms decaying per second, given by R = lambda x N. The number of atoms N is dimensionless (a count); activity R has units of Bq (per second).
