Physics-
General
Easy
Question
To determine the half- life of radioactive element, a student plots graph of ln
t. Here 
is the rate of radioactive decay at time t. If the number of radioactive nuclei of this element decreases by a factor of 
after 4.16 yr, the value of
is
- 8
- 7
- 4
- 8.5
The correct answer is: 8
= |Activity of radioactive substance|
Taking log both sides
Hence, ln
t graph is a straight line with slope-
.
From the graph we can see that,
Now applying the equation
nuclei decreases by a factor of 8.
Hence the answer is 8.
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