Question

The rate of decay of a radioactive element at any instant is $1000$ disintegrations per second. If the half life of the element is $1s$, then the rate of decay after $1s$ will be

• A. $500/s$
• B. $1000/s$
• C. $250/s$
• D. $2000/s$

Answer 1

The correct option is A $500/s$

The rate of decay at given instant is ${10}^3/s=1000/s$

Half life is: $1s$

So, after $1s$, fraction undecayed is $1/2$

As, rate of decay $\propto$ fraction undecayed,

The rate of decay after one second will be $(1000\times 0.5)/s=500/s$