NEET Physics Nuclei Questions Solved


A radioactive material has mean-lives of 1620 yr and 520 yr for α and β-emission. The material decays by simultaneous α and β-emission. The time in which 1/4th of the material remains intact is 

(a) 4675 yr                                 (b) 720 yr

(c) 545 yr                                   (d) 324 yr

λ=λ1+λ2=11620+1520=2.54×10-3 Yr-1

             t1/2=In2λ=272.8 yrs.

14th of the material remains intact after 2 half-lives.

Difficulty Level:

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