Question

Initially $480$ particles per minute are being emitted by a radioactive substance. This number reduces to $240$ after $2$ hours. The number of particles being emitted per minute after next $4$ hour will be

• A. $0$
• B. $60$
• C. $80$
• D. $120$

Answer 1

Answer: (B)

$60$

$t=0hrR=480part/min$
$t=2hrR=240part/min$

$t_{1/2}=2hr$

After $4hr$:
$t=6hrR=480\times (\frac{1}{2}{)}^3$
$R=60part/min$