Nuclear Physics — Science STD 10 — Question

Rutherford (Rd) : It is another unit of radioactivity. It is defined as the quantity of a radioactive substance, which produces $10^6$ disintegrations in one second.
$1 Rd =10^6$ disintegrations per second.
Becquerel $( Bq )$ : It is the $SI$ unit of radioactivity is becquerel. It is defined as the quantity of one disintegration per second.

Roentgen $(R)$ : It is the radiation exposure of $\gamma$ and $x$-rays is measured by another unit called roentgen. One roentgen is defined as the quantity of radioactive substance which produces a charge of $2.58 \times 10^{-4}$ coulomb in $1 kg$ of air under standard conditions of pressure, temperature and humidity.