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N
N
e
0
2592
0 0749
==
−
.
..
27. (a) The halflife
T
1/2
and the disintegration constant are related by
T
1/2
= (ln 2)/
λ
, so
T
1/2
= (ln 2)/(0.0108 h
– 1
) = 64.2 h.
(b) At time
t
, the number of undecayed nuclei remaining is given by
NN
e
N
e
t
tT
−
−
00
2
12
λ
ln
/
/
.
af
We substitute
t
= 3
T
1/2
to obtain
N
N
e
0
32
0125
−
ln
In each halflife, the number of undecayed nuclei is reduced by half. At the end of one
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 Spring '08
 Any
 Physics

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