Mean life is the time at which the number of nuclei falls to what fraction of its initial value?
AOne over e
BOne over pi
COne over ten
DOne over six
Answer & Solution
Correct answer: A. One over e
1. Mean life is a different measure from half-life.
2. It is defined by the natural exponential rather than by a half.
3. Mean life is the time at which the number of nuclei has been reduced to e to the minus one of its initial value.
4. So the answer is one over e.
_Source: NCERT Class XII Physics Part II, Ch 13 'Nuclei'_
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