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JAMB Physics 2022 Paper

Question : 12

Total: 40

Solution:

Concept:

Half-life is the time taken for a radioactive sample to reduce to half of its initial activity.

Explanation:

Initial activity,

A_0 = 120 \, \mathrm{Bq}

Activity after 6 days,

A = 15 \, \mathrm{Bq}

The activity left after

n

half-lives is given by:

A = A_0 \left(\frac{1}{2}\right)^n

Substitute the values:

15 = 120 \left(\frac{1}{2}\right)^n

\frac{15}{120} = \left(\frac{1}{2}\right)^n

\frac{1}{8} = \left(\frac{1}{2}\right)^n

Since

\frac{1}{8} = \left(\frac{1}{2}\right)^3

, we have:

n = 3

Total time taken is 6 days.

Therefore, half-life

= \frac{6 \, \text{days}}{3} = 2 \, \text{days}

Answer:

B. 2 days

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