Given, the sample has a half life of T years.
(a) The fraction of the original sample left is ,
=
Hence, there are 5 half lives of T years spent. Thus, the time taken is 5T years.
(b) The fraction of the original sample left =
i.e., = 100
n log 2 = log 100
Hence, n = = 6.64
From, t= nT we have, t = 6.64 T.
Hence, there are 6.64 half lives of T years spent. Thus, the time taken is 6.64T years.
(i)
(ii)
(iii)
(iv)
(v)
(vi)
(vii)
Given,
Half- life of = 28 years.
Using the formula,
90 g of Sr contains 6.023 x 1023 atoms.
15 mg of Sr contains,
Disintegration rate,