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AIPMT 2011 Physics and Chemistry Solved Paper
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© examsnet.com
Question : 57
Total: 100
The half life of a radioactive isotope '
X
' is 50 years. It decay to another element '
Y
' which is stable. The two elements '
X
' and '
Y
' were found to be in the ratio of
1
:
15
in a sample of a given rock. The age of the rock was estimated to be:
150 years
200 years
250 years
100 years
Validate
Solution:
Number of
X
:
N
x
Number of
Y
:
N
y
N
x
N
y
=
1
15
Part of
N
x
=
1
16
(
N
x
+
N
y
)
=
1
2
4
(
N
x
+
N
y
)
So total 4 half lives are passed so age of rock is
4
×
50
=
200
years
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