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Concepts Of Physics MCQ Edition [Volume 2]
Exam
Concepts Of Physics MCQ Edition [Volume 2]
Subject
Physics
Chapter
The Nucleus

Concepts Of Physics MCQ Edition [Volume 2] · Physics · The Nucleus

A vessel contains 4 × 10^ 23 tritium atoms. Given that the...

A vessel contains 4×10234 \times 10^{23} tritium atoms. Given that the half-life for the decay of tritium nuclei is 12.3 y12.3 \text{ y}, determine the activity of the sample.

Options

  1. A7.146×1014 disintegrations s−17.146 \times 10^{14} \text{ disintegrations s}^{-1}
  2. B1.429×1015 disintegrations s−11.429 \times 10^{15} \text{ disintegrations s}^{-1}
  3. C2.254×1016 disintegrations s−12.254 \times 10^{16} \text{ disintegrations s}^{-1}
  4. D3.573×1014 disintegrations s−13.573 \times 10^{14} \text{ disintegrations s}^{-1}

Correct answer

A. 7.146×1014 disintegrations s−17.146 \times 10^{14} \text{ disintegrations s}^{-1}

Step-by-step solution

The activity of a radioactive sample is given by the formula:

A=λNA = \lambda N

where λ\lambda is the decay constant and NN is the number of atoms.

The decay constant λ\lambda is related to the half-life T1/2T_{1/2} by:

λ=ln⁡2T1/2≈0.693T1/2\lambda = \dfrac{\ln 2}{T_{1/2}} \approx \dfrac{0.693}{T_{1/2}}

Given:

T1/2=12.3 y=12.3×365×24×3600 s=3.879×108 sT_{1/2} = 12.3 \text{ y} = 12.3 \times 365 \times 24 \times 3600 \text{ s} = 3.879 \times 10^8 \text{ s}

N=4×1023N = 4 \times 10^{23}

Substituting these values into the activity formula:

A=0.6933.879×108×4×1023A = \dfrac{0.693}{3.879 \times 10^8} \times 4 \times 10^{23}

A≈1.786×10−9×4×1023A \approx 1.786 \times 10^{-9} \times 4 \times 10^{23}

A≈7.146×1014 disintegrations s−1A \approx 7.146 \times 10^{14} \text{ disintegrations s}^{-1}
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