NEET Physics Nuclei Questions Solved

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NEET - 2013

The half-life of a radioactive isotope X is 20 yr. It decays to another element Y which is stable. The two elements X and Y were found to be in the ratio 1:7 in a sample of a given rock. The age of the rock is estimated to be

(a) 40 yr

(b) 60 yr

(c) 80 yr

(d) 100 yr

(b) As N/No=(1/2)n 


Number of half lices=3

=> T=20yr  

∴ T=t/n or t=T x n

=20 x 3yr=60yr

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