Atoms And Nuclei Question 406

Question: In an ore containing uranium, the ratio of U238 to Pb206 nuclei is 3. Calculate the age of the ore, assuming that all the lead present in the ore in the final stable product of U238 . Take the half-life of U238 to be 4.5×109 ear.

Options:

A) 1.8×109 year

B) 2.3×1010 year

C) 5.1×107 year

D) 6.2×106 year

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Answer:

Correct Answer: A

Solution:

  • Suppose x is the number of Pb206 nulei.

The number of U238 nuclei will be 3x, Thus 3x+x=N0 We know that

N=N0eλt or 3x=4xeλt
eλt=43

or t=In,4/3λ=Im4/3(0.693/t1/2) =In4/3(0.693/4.5×109)=1.868×109 years.



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