InterviewSolution
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InterviewSolution
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(a) Calculate the activity of one mg sample `._(28^(Sr^(90)))` whose half life period is `28` years. (b) An experiment is performed to determine the half-life of a radioactive substance which emits one beta particle for each decay process. Observation shown that an average of `8.4 beta-`particles are emitted each second by `2.5 mg` of the substance. the atomic weight of the substance is `230`. calculate the half0life of the substance. (c) Determine the quantity of `._(84^(Po^(210)))` necessary to provide a source of alpha particle of `5mCi` strength (`T_(1//2)` for Po `= 138` day). |
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Answer» (i) number of atoms `,N=("Mass")/("Atomic weight"xxN_(A),` (where `N_(A)` is Avogadro number ) `=(2xx10^(-3))/(90)xx6.023xx10^(23)` `=13.38x10^(18)` Decay constant ,` lamda =("in "2)/(T_(1//2))=(0.693)/(287)//yr` Activity ,`R=lamda N=(0.693)/(28)xx13.38xx10^(18)` `=0.331xx10^(18)//yr` `=(0.331xx10^(18))/(365xx24xx3600)=10^(10)`dps (ii) Half -life of the substance `N=(2.5xx10^(-3))/(230)xx6.023xx10^(23)=6.5xx10^(18)` Activity `,R=8.4//s =lamda N =("in2")/(T_(1//2))Nimplies T_(1//2)=("in2")/(A)N` , half -life of the substance `T_(1//2)=(0.693xx6.5xx10^(18))/(8.4)` `=0.54xx10^(18)s=1.7xx10^(10)yr` |
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