1.

At a certain instant a piece of radioactive material contains 10^(12) atoms. The half-life of the material is 30 days. What will be number of distingrations per second of the sample at that instant?

Answer»

`3.96 xx 10^(6)` dps
`4.02 xx 10^(5)` dps
`2.66 xx 10^(5) ` dps
`1.96 xx 10^(6)` dps

Solution :`t_(1//2) = 30` days
`N_t = 10^(12)` ATOMS
Now `lambda = (0.693)/(t_(1//2)) = (0.693)/(30) "days"^(-1)`
Again RATE of distintegration of the sample is,
`(-dN_t)/(DT) = lambdaN_t = (0.693)/(30) xx 10^(12)`
`= 2.31 xx 10^(10)` disintegrations per day = `2.66 xx 10^(5) dps`.


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