Question

A human body required $0.01M$, activity of radioactive substance after $24$ hours. Half life of radioactive substance is $6$ hours. Then injection of maximum activity of radioactive substance that can be injected.

• A. $0.08M$
• B. $0.04M$
• C. $0.16M$
• D. $0.32M$

Answer 1

The correct option is C $0.16M$

We are given, Half life = 6 hours

Number of half life(n) in 24 hours = $\frac{24hr}{6hr}$ = 4

The activity after 4 half lives = 0.01

The initial activity of the sample can be calculated as:

Activity after 4 half lives = Initial Activity $\times$ $[\frac{1}{2}{]}^n$

0.01 = Initial Activity $\times$ $[\frac{1}{2}{]}^4$

Initial Activity = $0.01\times 2^4$ = 0.16