Modern Physics> Sir, please solve: At a certain instant, ...

Sir, please solve:
At a certain instant, a piece of radioactive material contains 10¹²atoms. The half-life of the material is 30 days.
(i) Find the number of disintegrations in the first second.
(ii) What time would elapse before 10⁴atoms remain?
(iii) What is the count rate after this time?

Utkarsh Shukla , 11 Years ago

Grade 12

2 Answers

Abhishek Kumar

half life = 1/ $\lambda$
so, $\lambda$ = 1/(30 X24 X 60 X 60)
So, 1) dN = $\lambda$ x 10¹² x1 ( $\lambda$ Ndt)
2) If N = 10⁴ = 10¹² e^-t
Solve for t, rest things are known.
3) Count rate = $\lambda$ N = $\lambda$ 10⁴

Last Activity: 11 Years ago

Fareena

1) lambda= 0.693/t(1/2)

lambda = 0.693/30 t(1/2)=30 days (given)

lambda = 0.0231/day

-dN/dt= N lambda

= 10^12 × 0.0231

= 2.31 × 10^10 disintegration/day

= 2.31×10^10 ÷ 24×3600

= 2.7× 10^5 disintegration/second

Last Activity: 5 Years ago

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Modern Physics> Sir, please solve: At a certain instant, ...

Sir, please solve:At a certain instant, a piece of radioactive material contains 1012 atoms. The half-life of the material is 30 days.(i) Find the number of disintegrations in the first second.(ii) What time would elapse before 104 atoms remain?(iii) What is the count rate after this time?

Utkarsh Shukla , 11 Years ago

Abhishek Kumar

Fareena

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Sir, please solve:
At a certain instant, a piece of radioactive material contains 10¹²atoms. The half-life of the material is 30 days.
(i) Find the number of disintegrations in the first second.
(ii) What time would elapse before 10⁴atoms remain?
(iii) What is the count rate after this time?

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