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PhysicsInteger+4Question 44 of 69

IIT-JEE 2011 · Paper 1, Physics question 44

The activity of a freshly prepared radioactive sample is 101010^{10} disintegrations per second, whose mean life is 10910^9 s. The mass of an atom of this radioisotope is 10−2510^{-25} kg. The mass (in mg) of the radioactive sample is

Answer and worked solution

Official answer: 1

Number of atoms. A=λN=NτA=\lambda N=\dfrac N\tau, so N=1010×109=1019N=10^{10}\times10^9=10^{19}.

Mass. 1019×10−25=10−610^{19}\times10^{-25}=10^{-6} kg = 1 mg.

Answer: 1

Topics:Radioactive decay
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