An accident in a nuclear laboratory resulted in deposition of a certain amount of radioactive material of
half-life 18 days inside the laboratory. Tests revealed that the radiation was 64 times more than the
permissible level required for safe operation of the laboratory. What is the minimum number of days after
which the laboratory can be considered safe for use?
(A) 64 (B) 90
(C) 108 (D) 120
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12th
Physics
Nuclei
First Order Radioactive Decay
An accident in a nuclear la...
PHYSICS
An accident in a nuclear laboratory resulted in deposition of a certain amount of radioactive material of half-life 18 days inside the laboratory. Tests revealed that the radiation was 64 times more than the permissible level required for safe operation of the laboratory. What is the minimum number of days after which the laboratory can be considered safe for use?
October 15, 2019
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Maninder Dobhal
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VIDEO EXPLANATION
ANSWER
Given : T
1/2
=18 days
Let the permissible activity after time t be R
o
⟹ Initial activity of the radiation, R=64R
o
Using :
T
1/2
0.693
t=2.303log
10
R
o
R
∴
18
0.693
t=2.303log
10
(64)
18
0.693
t=2.303×1.806 ⟹t=108 days