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UPSEE Solved Model Paper 3
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© examsnet.com
Question : 9
Total: 150
The half lives of radioisotopes
P
32
and
P
33
are 20 days and 30 days respectively. The radioisotopes are mixed in the ratio of 4 :1 of their atoms. If the initial activity of the mixed sample is 7m Ci, then the activity of the mixed isotopes after 60 days.
2.5m Ci
1m Ci
3.2m Ci
3m Ci
Validate
Solution:
As,
N
32
N
33
=
4
1
[
N
33
=
N
0
]
⇒
d
N
N
=
λ
1
N
32
+
λ
2
N
33
⇒
7
×
10
−
3
=
λ
14
N
0
+
λ
2
N
0
⇒
7
×
10
−
3
=
N
0
[
l
n
(
2
)
5
+
l
n
(
2
)
30
]
⇒
N
0
−
30
×
10
−
3
l
n
(
2
)
After 60 days,
d
N
d
t
−
λ
1
4
N
0
8
+
λ
2
N
0
4
−
1
m
C
i
© examsnet.com
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