Question

The SI unit of radioactivity is:
A. curie
B. becquerel
C. juliot
D. ${{\text{s}}^{\text{-1}}}$

Answer 1

Hint: Here we are talking about the nuclear phenomenon which emits radiation during the decay and thus has it's different units in which it is measured. But primarily here we will focus on it's SI unit and try to relate it with other composite units.

Complete step by step solution:
Let's first try to understand radioactivity:
-Radioactivity is basically a process of spontaneous emission of alpha, beta and gamma particles from their nuclei when the atom becomes unstable.
- The radiation coming out from this phenomenon was earlier known as Becquerel rays.
- Traditionally the amount of radioactivity present was estimated by the number of curies(Ci) present, as the more the curies, more was the radioactivity emitted.
- But The Systeme International of units(SI system), uses the unit of Becquerel (Bq) as it's unit of radioactivity.
- One becquerel is defined as the activity of a quantity of radioactive material in which one nucleus disintegrates per second.
- 1Bq = 1per second
- But we generally use the multiple units other than Becquerel commonly to estimate the decays per second.
-So we will consider Becquerel as our correct answer which is an option.

Additional Information:
-The becquerel succeeded the older unit of Radioactivity that is Curie(Ci).
-One curie is 37 billion Bq.
- As the Bq generally represents a small amount, we generally use a large multiplier with the Bq as follows:
37 GBq = 37 billion Bq = 1 curie
- 1 becquerel= 1 radioactive decay per second= $\text{2}\text{.703 }\!\!\times\!\!\text{ 1}{{\text{0}}^{\text{-11}}}$
- Curie is also defined as the quantity of any radioactive substance which will give us $\text{3}\text{.7 }\!\!\times\!\!\text{ 1}{{\text{0}}^{\text{10}}}$disintegration per second. Another unit that we use is Rutherford (rd) which is defined as the amount of radioactive substance giving $\text{1}{{\text{0}}^{\text{6}}}$ disintegration per second.

Note: There are multiple units of radioactivity that we use while solving numericals or related problems, but one thing that should be remembered is that we should always know the various conversions of units to Becquerel, as it is the standard unit.