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Engineering Entrance Exams

Radioactivity of a sample (z=22) decreases 90% after 10 years. What will be the half life of the sample? (A) 5 years (B) 2 years (C) 3 years (D) 10 years

Profile image of aniket anand
12 Years agoGrade
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2 Answers

Profile image of Arun
6 Years ago

t=10 yr, t21=?

λ=t2.303logNtN0

Since, radioactivity decreases 90% in 10 yr.

N0=100

and Nt=10

Thus, λ=102.303log10100

or λ=102.303

since, t31=λ0.693

t21=2.3030.693×10

=3 yr

 

Hence option C is correct


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