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AIEEE 2007 Solved Paper
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© examsnet.com
Question : 25
Total: 118
A radioactive element gets spilled over the floor of a room. Its half-life period is 30 days. If the initial activity is ten times the permissible value, after how many days will it be safe to enter the room?
1000 days
300 days
10 days
100 days
Validate
Solution:
Suppose activity of safe working
=
A
Given
A
0
=
10
A
λ
=
0.693
t
1
/
2
=
0.693
30
t
1
/
2
=
2.303
λ
log
A
0
A
=
2.303
0.693
/
30
log
10
A
A
=
2.303
×
30
0.693
×
log
10
=
100
days.
© examsnet.com
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